Combine all the ingredients except nutella in a mixing bowl

Beat the mixture until smooth and with no butter lumps

Pour half of your mixture in a rectangular baking tin

Put a tablespoon of nutella, swirl it with a fork

Pour the other half

Put another tablespoon of nutella, swirl it.

Bake at 160° 60 minutes

Put a clean knife through of it comes out clean its cooked if not let it bake for another 5 minutes