Cream butter and sugars until completely combined, then crack in eggs, one at a time. You want to scrape sides now and then.
Mix in flour mixture until completely combined, then divide batter into 2. Leave one bowl as is, while adding cocoa powder to the other. Batter will be thick.
Grease and flour your mold generously, and preheat your oven to 350 F
Drop batter one heaping tbsp per flavor, alternating one after another, creating a marble effect
Tap mold on flat surface a couple of times, then bake for 50-55 minutes, depending on your oven (I used convection oven, and it was for 45 mins)
Flip cake on a cooling rack, slice and enjoy, when you are ready