Gugelhupf Cake

Preheat your oven to 170°C / 340°F and coat the bundt pan with melted butter.

Whisk the butter with the egg yolk until foamy, add icing sugar, and stir until creamy. Add vanilla extract or sugar.

Beat the egg whites until stiff. Sift together the flour and baking powder. Mix half of the flour into the butter mixture and combine. Add the milk, combine, then add the remainder of the flour.

Pour less than half of this mixture into the pan. Add cocoa to the rest and mix. Pour the darker batter on top of the lighter one into the pan.

Drag the handle of a wooden spoon or a regular fork through the batter in a wave-like motion to achieve the marble texture.

Bake for 50 to 55 minutes. Let cool for a few minutes, then remove the cake from the pan and dust it with icing sugar.