Separate the eggs. Beat the egg whites with the powdered sugar and vanilla sugar until very stiff.
Beat oil and egg yolks until creamy. Stir in flour, baking powder, custard powder. Fold in stiffly beaten egg whites.
Pour the mixture into a greased and floured pan or a pan lined with baking paper and bake in a preheated oven at 180 °C for approx. 45 minutes.
Test with a needle! When the dough no longer sticks to the needle, the cake is ready.
Sprinkle cake with powdered sugar.