For the lemon cake, put the sugar, butter, eggs and vanilla sugar in a bowl and mix vigorously.
When everything is nice and creamy, add the flour and baking powder.
Finally, add the grated zest of one lemon. Pour the thick batter into a loaf or loaf pan that has been well greased with butter.
Bake the lemon cake in a preheated oven at 170° C for about 45 minutes.