Mix the soft margarine with the sugar until frothy, gradually add the eggs. Mix the flour with the baking powder and stir in. Add the orange juice. Put half of the batter in a second bowl. Mix one half with the orange peel, stir the cocoa and Nutella into the other half.
Grease a loaf pan or Gugelhupf pan. Pour alternately light and dark dough and marble with a fork.