For the oil cake, separate the eggs. Squeeze lemon and grate peel. Cream oil, water, powdered sugar, vanilla sugar, lemon juice, lemon zest and yolks in a food processor.
Mix baking powder and flour well. Beat egg whites until stiff. Fold both into the mixture. Preheat oven to 150°C. Grease the cake pan and dust with flour. Pour in the mixture and bake for approx. 60 minutes.
Increase the heat to 180°C constantly. Check whether the cake is an oil cake with the help of a test stick.