How to make a marbled bicolour donut cake?

• Before starting, weigh and prepare all ingredients on the work surface. Sift the flour and baking powder "Pane degli Angeli" into a bowl. In a small bowl, set aside the unsweetened cocoa powder which will be the last ingredient we will use.
• In a larger bowl, break the eggs, add sugar and whisk with an electric mixer for at least 3 minutes and up to 10 minutes. Add oil and milk to the mixture. Also, add the sifted flour with the baking powder and mix well with a spatula, making slow movements from bottom to top to avoid breaking the eggs.
• Butter the aluminum donut cake pan, any 22 cm to 26 cm diameter pans will work. Divide the donut cake dough, and in one of the two bowls, add the unsweetened cocoa powder. We recommend using Perugina unsweetened cocoa powder, which gives a really chocolatey final colour and has a more intense flavour.
• Pour the two batters into the pan, releasing your imagination: for a bicolour donut cake, first pour all the white batter, then all the cocoa batter; for a marbled donut cake, pour a little white batter and then use the unsweetened cocoa batter to create random lines in the batter, pour white batter again and then the dark one until both are finished; for a striped donut cake, pour a layer of white batter and an equal amount of cocoa batter, repeat alternately until both bowls are empty.
• Now that we had fun pouring the batters into our favourite donut pan, bake our two flavour cake in a preheated oven at 356°F for about 40 minutes. Always do the toothpick test before taking it out of the oven (the toothpick should come out completely dry).
• After finishing baking, let it cool down before slicing your bicolour donut cake and serving! You can add powdered sugar, but it's already beautiful and delicious as it is! ps: the calories refer to 100 g of bicolour donut cake.