Beat in mixer the eggs and sugar for 15 minutes. Place the mixer on low. add oil slowly and orange juice.
Put the mixer on the lowest setting and add flour, baking powder and vanilla sugar. Mix for 2 seconds. Turn the mixer off and mix using a spatula. Pour mixture into baking pan leaving 6+ tblsp behind. now add the cocoa, mix then add it to pan mixing with a fork to get marble affect.
Pour the batter into the baking pan leaving 6+ tblsp behind. Add the cocoa to the 6 tablespoons, mix then add it to pan mixing with a fork to get marble affect.
Bake on 180C (350F) for 45 minutes, check after 40 mins-poke with fork to see if ready.