Preparation time: 10 minutes
Baking time: 50 minutes
 

1. Melt the butter. Combine the flour and baking powder. Separate the eggs. Beat the egg whites with a pinch of salt to stiff peaks. Preheat the oven to 150° C (300° F).
2. Mix the sugar into the yolks until creamy. Add alternately the flour-baking powder mixture and melted butter until both are incorporated. Gently fold in the egg whites.
3. Divide the batter between two bowls. Into one, mix in the vanilla sugar; into the other the cocoa.
4. Alternate pouring the two batters into a buttered loaf pan.
5. Bake in the preheated oven for about 50 minutes. The cake is done when a knife blade inserted in the middle comes out clean.