Directions

1. In a bowl, combine the eggs and the sugar, and beat with an electric mixer until creamy and fluffy. Add the butter and vanilla and stir well.
2. Gradually add the flour with the baking powder and the buttermilk, and beat well until homogeneous.
3. In a separate bowl, combine the cocoa and the water and mix well. Add slightly more than 1/3 of the cake batter to the cocoa and stir well, thus obtaining two batters, yellow vanilla and brown chocolate.