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
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
- 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 ⅓ 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.
- Set one layer of cake on a serving platter and spread the top with about ⅓ 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!