Preheat the oven to 180º C (356F)
Beat the softened butter with stevia and vanilla powder. Add sour cream and keep mixing.
Start adding eggs, one by one and keep mixing. make sure the mixture is smooth.
Combine almond and coconut flour with baking soda and psyllium. This will be your dry ingredients mixture.
Combine cacao with cinnamon, apple cider vinegar, and red food colouring and mix well until you get a smooth mixture.
Start adding the dry ingredients mixture, spoon by spoon to the batter. Keep mixing.
Add cacao mixture in the end and mix for another 3 minutes.
grease the 25 cm (8-inch) cake mould with some butter and sprinkle with raw cacao powder. Pour in the batter and bake it in the oven for 20 minutes.
In the meantime, prepare the cream by mixing mascarpone, vanilla, lemon juice and mineral water. Keep mixing until the cream becomes fluffy and not too firm.
When the cake is baked, let it cool down a bit, remove it from your cake mould and cut it in half.
Use one part of the cream to fill the cake and cover the top of the cake with the rest of the cream. Leave the sides uncovered. You can decorate the cake with raw cacao, or cut a thin layer out of your cake, crumble it and use as cake decoration.
Serve well chilled!