Preheat oven to 325F and grease a large bundt pan (9 to 10 inches in diameter) well. I like to double grease (working butter into the pan first and then spraying with coconut oil or avocado oil spray).
In a large bowl, whisk together almond flour, sweetener cocoa powder, coconut flour, whey protein, baking powder, salt, and xanthan gum
Add the eggs, melted butter, vanilla extract and ⅔ cup of the water. Add the If your batter is very thick add additional water, 1 tablespoon at a time, until it thins out. It should be spreadable but not pourable.
Spread batter in the prepared pan and smooth the top. Bake 45 minutes or until set and a tester inserted in the center comes out clean.
Let cool in the pan 30 minutes, and then flip out onto a wire rack to cool completely.
In a small saucepan over medium heat, bring the raspberries and water to a boil. Cook about 5 minutes, until the berries can easily be mashed. Strain through a sieve into a bowl, pressing on the solids to extract as much juice as possible.
In a large bowl, beat the cream cheese, butter, and sweetener together until smooth. Beat in the raspberry juice and the extracts. If the frosting is stiff, beat in the heavy cream. DO NOT ADD THE WATER YET!
To Fill the Cake:
Flip the cake over carefully onto a plate to cut a trench in the bottom. You will cut a trench about 1 ½ inches wide in the bottom of the cake, and about 1 ½ inches deep. Use a sharp knife to cut at an angle so that you can lift whole sections of the cake out intact (you will need pieces of it to cover the filling before flipping the cake back over).
Use a spoon to scoop out more of the cake so that the trench is rounded at the bottom. In the end you want the trench to be about 1 ½ to 2 inches deep. Fill the trench with raspberry frosting, almost but not quite to the top (you will only need about a cup or so of frosting to fill the cake).
Cut the very tops from the pieces you cut out and use those to cover the frosting in the trench. Press down to get it firmly in there. Then cover the bottom of the cake with a serving plate and flip the whole thing back over.
To Frost the Cake:
Make the chocolate buttercream as directed and all over the entire cake, even inside the hole of the bundt.
Whisk water 1 tablespoon at a time into the remaining raspberry frosting, until it is thick but pourable. Spoon it over the cake and let drip thickly down the sides. Add a few fun sprinkles and refrigerate at least 2 hours.
This is a big, filling cake. Although I've said it serves 16, it could easily serve 2o if you are serving with a bit of keto ice cream!