Mix the butter with sugar until blends well. Add the eggs. Mix to incorporate. Add half the flour and incorporate. Add half the milk and incorporate. Add vanilla extract and baking powder. Stir in the rest of the flour and milk. Incorporate well everything.
Line and grease with butter 2 baking pans. Pour in the batter reserving 3-4 tablespoons. Add in the cocoa and 3 tbsp milk to obtain the cocoa batter.Place some sour cherries on the white batter, pour over the cocoa batter and make swirls with a spoon or a fork. Add more sour cherries on top and bake at 350° F for 45 minutes or until done.Let the loaf cakes cool on a rack wire until completely cooled. Decorate with icing sugar if you like, slice and enjoy!