Beat the sugar & eggs until frothy. Fold in the oil, orange juice, flour and baking powder. Divide the dough into 3 parts!
Pour 1/3 of the dough into the baking pan (of your choice), mix 1/3 with the 2 tablespoons of cocoa powder and let it flow into the mold, mix 1/3 of the dough with the ground hazelnut kernels and also let it flow into the mold.
The cake has to bake for about 1 hour at 180 degrees, test with wooden sticks!