Keto marble cake doesn’t get any better than this! Two layers of low carb vanilla and chocolate cake swirled together, with a silky smooth low carb chocolate frosting. A perfect keto birthday cake recipe. This post is sponsored by Bob’s Red Mill.
I am currently obsessed with gorgeous layer cakes. Not so much with eating them, although of course I enjoy that too. But with creating them, and with finding ways to take keto cake baking to new heights. It’s just ever so satisfying and amazing when I can create a keto birthday cake like this one and have it rival any high carb, high sugar recipe.
This keto marble cake is something I created for my daughter’s birthday, and it is spectacular, if I do say so myself. The cake alone is delicious, but then I topped it all off with a chocolate version of my sugar-free Swiss Meringue Buttercream. And my decorating wasn’t half bad either, this time around!
Marble Cake Recipe Inspiraton
I have made a few keto marble cake recipes, including a peanut butter marble bundt cake, and a marble loaf cake.
But after spotting a few gorgeous marble layer cakes on Pinterest, including this one from Baking a Moment, I just had to try my hand at a keto version. Allie is an talented pastry chef that I’ve known online for years now, and her recipes are always simply gorgeous. So I sweet-talked my daughter into letting me make this for her 13th birthday.
One of the tricks I learned from this recipe was incredibly helpful, and that was to mix the cocoa powder with hot water before creating the chocolate batter. Heretofore, I’ve always just added the cocoa powder straight into the vanilla batter, which makes it incredibly thick and harder to work with.
I also knew I wanted Chocolate Swiss Meringue Buttercream for the frosting. I can’t tell you just how amazing Swiss Meringue is compared to regular buttercream. It’s so silky smooth, and so easy piped, it’s ideal for cake decorating. While my classic keto chocolate frosting is easier to make, it isn’t quite the same.
How to make Marble Cake
It isn’t difficult to make a keto marble cake but it does take a bit more effort than some cakes – and it’s worth it. It’s a fun one to bake and looks particularly amazing when you slice into it. Here are a few pointers to getting it perfect.
Which keto flour?
I used all almond flour for this cake recipe, so it’s entirely coconut-free for those of you who are allergic or simply don’t like coconut. However, I know some of you will ask how it can be made with coconut flour instead. Please understand that this is not a direct exchange.
For a nut free version, I recommend following my keto coconut flour cupcakes recipe, and using hemp milk or dairy milk in place of the almond flour. Then proceed to add the cocoa powder and water as you would in the recipe here.
Adding protein powder
This is an important ingredient, as it replaces gluten and helps the cake rise and hold its shape. You can use egg white protein in place of the whey, if you prefer. But please do not use collagen or bone broth protein, as it makes baked goods gummy and hard to cook through.
Always line your pans with parchment
Trust me, it will save you so much grief! Even if your cake layers stick a bit to the sides of your pans, you can still run a sharp knife around them to get them out. But parchment liners will keep the cake from sticking to the bottoms, and you will be able to get them out in one piece.
To cut down on prep, I highly recommend these parchment circles for your cake pans.
How to marble the batter
Keto cake batter is always thicker than conventional batters, so marbling them nicely is a bit trickier. I recommend add the batters in small alternating dollops, about 2 tablespoons at a time. Once you have one layer in the pan, swirl it together with a knife, lifting sometimes from the bottom to mix them up more. Then smooth the top as best you can.
How to make Chocolate Swiss Buttercream
I promise it’s not as difficult as it seems at first. It’s actually remarkably forgiving too. Simply follow the steps for my sugar-free swiss buttercream and simply drizzle in melted dark chocolate toward the end.
I did find that at first my buttercream was too soft to spread on the cake so I placed it the whole bowl in the fridge for 10 minutes to firm it up a bit.
How to decorate a keto marble cake
Now for the fun part! I held back some of my frosting so that I could pipe pretty rosettes onto the top of the cake. Then I topped each rosette with a mini keto chocolate chip cookie.
But you could also add some fun sugar-free sprinkles instead. Or simply shave some sugar-free dark chocolate overtop. Have some fun with it!
More Amazing Keto Layer Cakes
- Keto Caramel Cake
- Keto Italian Cream Cake
- Keto Victoria Sponge Cake
- Classic Carrot Cake with Ginger Cream Cheese Frosting
- Low Carb Zucchini Layer Cake
- Keto Tiramisu Layer Cake
Marble Layer Cake
Ingredients
Cake
- 3 cups almond flour
- 1/3 cup whey protein powder
- 1 tbsp baking powder
- 1/4 tsp salt
- 1/2 cup sour cream
- 3/4 cup Swerve Sweetener
- 3 large eggs, room temperature
- 2 tsp vanilla extract
- 1/2 cup unsweetened almond milk
- 1/3 cup cocoa powder
- 1/3 cup hot water
Chocolate Swiss Buttercream
- 4 ounces sugar-free dark chocolate, chopped
- 1 recipe Swiss Meringue Buttercream
Instructions
- Preheat the oven to 325F and grease 2 8-inch round baking pans. Line the bottoms of the pans with parchment and grease th parchment.
- In a medium bowl, whisk together the almond flour, whey protein, baking powder, and salt. Set aside.
- In a large bowl, beat the sour cream with the sweetener until well combined. Beat in the eggs and vanilla extract. Add half of the almond flour mixture and beat until combined, then beat in the almond milk. Beat in the remaining almond flour until the batter is well combined. If it's very thick, add another tablespoon or two almond milk. It should be spreadable but not pourable.
- In another large bowl, whisk the cocoa powder and hot water together until smooth. Add about 1/3 of the vanilla batter to the cocoa mixture and stir until well combined.
- Add the two batters in small alternating dollops to the two pans and swirl with a knife, then smooth the tops. Bake 25 to 30 minutes, until the edges are set and the tops are just firm to the touch.
- Remove and let cool completely in the pans, then flip out onto a wire rack and remove the parchment.
Chocolate Swiss Buttercream Frosting
- Set a heatproof bowl over a pan of barely simmering water. Add the chopped chocolate and stir until melted and smooth. Remove from over the pan and let cool while preparing the rest of the frosting.
- Prepare the Sugar-Free Swiss Buttercream according to the directions. After all the butter has been added, set the mixer on low and drizzle in the melted chocolate until combined. You will need to stop the mixer and scrape the sides and bottom with a rubber spatula a few times to get all the chocolate mixed in.
- Note: if your frosting is super soft after adding the chocolate, simply place in the fridge for about 5 to 10 minutes to firm up a little before frosting the cake.
To assemble
- Set one layer of cake on a serving platter and spread the top with about 1/3 of the frosting. Place the second layer on top and spread the top and sides with more frosting. There should be enough to pipe some rosettes on the top as well, if desired.
- Decorate with mini keto cookies or small pieces of sugar-free chocolate. Or consider adding some sugar-free sprinkles!
Nutrition
Nutritional Disclaimer
Please note that I am not a medical or nutritional professional. I am simply recounting and sharing my own experiences on this blog. Nothing I express here should be taken as medical advice and you should consult with your doctor before starting any diet or exercise program. I provide nutritional information for my recipes simply as a courtesy to my readers. It is calculated using MacGourmet software and I remove erythritol from the final carb count and net carb count, as it does not affect my own blood glucose levels. I do my best to be as accurate as possible but you should independently calculate nutritional information on your own before relying on them. I expressly disclaim any and all liability of any kind with respect to any act or omission wholly or in part in reliance on anything contained in this website.
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Is there a keto chocolate icing recipe you recommend that is egg free? I can tolerate them baked in, but a merengue is more than I can handle.
https://alldayidreamaboutfood.com/low-carb-chocolate-frosting/
Hi Caroline! I’m wondering if it makes a difference if I use whey protein vs whey protein isolate ?
It’s not enough to make much difference in baking.
Wonderful! Thanks so much!
Hello! I just made the cake and looks pretty nice, just wondering how to store it, fridge or room temperature?
Thanks
Cakes with frosting should always be refrigerated but I like to serve them at room temp for softer frosting.
Thanks Caroline! I will do that
This is my go-to cake. (Thank you). I have made into a two tier, vanilla icing, chocolate icing…and today a new twist. I had bought my husband a Lily’s Cookies and Cream white chocolate bar and used that instead of the 4 oz of chocolate in the icing. WOW! Thank you so much for sharing such reliable, delicious recipes!
Hi Carolyn,
My son has requested marble cupcakes instead of a cake for his birthday! Any advice on how long to cook?
Many thanks,
Katy
Just look at one of my other cupcake recipes as a rough guide.
We loved the keto marble cake, but the cake was a bit dry and crumbled too much when I frosted it. What did I do wrong? What can I add or change to make it cling together better? BTW, the Swiss meringue was awesome!
Sounds over-baked. What sweetener did you use?
Best low carb cake I have ever tried!
Thank you for sharing the recipe! It was so delicious! My family didn’t even notice it was Keto!
Your recipes so far are he best low carb/keto.
Is too bad I can post the picture of my cake.
Hi Carolyn! This sounds so yummy! I’m just wondering if I can replace the sour cream? I can’t find it anywhere in my country (Venezuela) we have whipping cream, Greek yogurt.. can I replace it with any of these? If so, what’s would the ratio be?
Thanks in advance! Looking forward to try out the recipe!
Greek yogurt is your best bet, and it’s the same amount.
So excited to try this! Fingers crossed the SMBC goes okay, it looks absolutely divine, your piping is just so beautiful. One question please – Can I use unsweetened 100% chocolate for the frosting along with the SMBC or will the higher cocoa content of this cause it to seize when I mix it in? I do have one pack of Lily’s Dark Chocolate Chips (not easy or cheap to find in the UK!) but I was hoping to save that for a recipe that uses chocolate chips. I also have some of your wonderful erythritol sweetened chocolate chips that I made some time ago. Should I use that instead of a bar of 100% chocolate? Or will the 100% chocolate be okay with some additional sweetener? Thanks!
I honestly cannot say since I haven’t tried it myself with unsweetened chocolate.
No worries, thank you very much for the quick response, Carolyn. I will use the Lily’s Chocolate Chips just to be on the safe side – all for a good cause (i.e. cake). I don’t want to risk ruining that beautiful frosting! I will let you know how this goes – can’t wait 🙂
PS. On another note, we will be making pork ribs with your dry rub this weekend (https://alldayidreamaboutfood.com/best-low-carb-barbecue-ribs/) and your Chipotle whisky barbecue sauce (https://swervesweet.com/recipes/chipotle-whiskey-barbecue-sauce), they both look delicious!
I finally made this recipe this week and had so much fun with it 🙂 This was my second time making your SMBC and this time it worked perfectly, no disasters other than my arm aching! The cake itself was a breeze to make, although my batter was significantly runnier than described in your recipe (maybe due to the brand of whey protein I used?), so instead of swirls I ended up creating alternating concentric circles of brown and white batter, didn’t look too bad at all! The texture of SMBC is just divine, but I found it a bit too sweet, even with Lily’s dark chocolate chips, so next time I might take the plunge and try 100% unsweetened chocolate (or maybe try a mocha flavoured frosting as described in the Handle The Heat blog linked to your SMBC recipe. It’s just a personal preference, but I prefer intensely dark chocolate frostings/ganache to milk chocolate, but my husband certainly liked this. Thank you again for your wonderful blog posts and detailed, tried and tested recipes, they are such a joy to make.
Hello again! By special request, I have been asked to make this for my friends next week, and I am so looking forward to giving this a go again 🙂 I do have a question, please – can this be made with hazelnut flour instead of almond flour, or perhaps a mix of both? Chocolate and hazelnuts do go so well together, I am hoping this will work. I am running low on almond flour and may not be able to buy enough in time, hence the hope that hazelnut flour will suffice. I would appreciate your thoughts.. thanks!
I made this once more, using almond flour again (not wanting to risk it failing with hazelnut flour), and 12ml double cream mixed with around 100ml water to replace almond milk. Again my batter was very runny, so I’m convinced it must be a protein powder brand thing (maybe what we get in the UK is made differently to the US? What brand do you use, please?). Nevermind, it still looks so pretty and I make concentric white-brown circles instead of swirls.
For assembly, as I was to be travelling with this cake, I used two 8″ square pans instead of round, baked for slightly less time, and then cut each cake into half (to get 4 rectangles) and frosted the layers in between, leaving the marbled top bare so that it was easier to pack in a box and carry. Worked a treat! 🙂 For the SMBC I used 100% chocolate (unsweetened) and it was still plenty sweet, so I’ll stick to this version next time – no seizing, no problems! Just aching arms again.. lol! Thank you again, Carolyn, this is such a special cake to make and eat!
Hi! I have some questions about the chocolate Swiss Buttercream Frosting. I would really love to use Valrhona Powdered Cocoa as my chocolate. Not being a baker I don’t have a CLUE how to successfully do it!!! Do you have any ideas? Also, I would like to make this frosting and, actually the cupcakes, several days before the event. But I would like to frost and decorate them the day of… Any suggestions? Can I successfully pipe this frosting chilled or do I need it to come to room temperature? Thanks so much for your time and efforts here!!! This will not be the first recipe I have tried???
If you are asking to sub cocoa powder for unsweetened chocolate, you can google that online, there is a specific formula. You cannot pipe any frosting chilled, so yes, you will have to bring it to room temperature.
Hi, Carolyn!!!
Thanks so much for your reply!!! I have decided that bar chocolate will be more flavorful. But, my ocd vision is to have a darker brown Swiss buttercream frosting to sprinkle golden mica glitter on… This is for a wedding… Any thoughts? By the way… I have 2 of your books THE ULTIMATE GUIDE TO KETO BAKING and EVERYDAY KETO KITCHEN… I have tried recipes and drooled over every one!!! Thanks so much for sharing with all of us!!!