Beat the soft butter with the sugar until you get a fluffy cream. While stirring, add the egg yolks one by one and then the milk and vanilla. Finally, add the flour, baking powder and raisins and mix well. Separately, beat the egg whites into hard snow, then mix them with the coconut flour, and set a little aside for decoration.
Gently mix the egg white-coconut mixture into the cake one, until you get a smooth coconut dough. Grease and flour a cake pan or a suitable tray. Pour in the mixture and gently smooth it.
Put the sponge cake to bake in a moderately heated oven to full readiness. Afterward, remove the baked sponge cake with coconut flour from the tray. Optionally, smear with a jam of your choice and sprinkle it with coconut flakes.