Wash the lemons with hot water, dry them and rub the peel off.
Put the flour, tartar baking powder (has no aftertaste), sugar and vanilla sugar in a bowl and mix together.
Please take both baking powder packets, because they ensure that the cake is just as fluffy as usual with eggs. Add the softened butter or margarine and mix with the hand mixer. Slowly stir in the milk and add the lemon zest. Mix everything well, the dough has to be hard to tear off the spoon.
Spread the dough on a greased baking sheet or lined with baking paper and bake in a preheated oven at 200 ° C top / bottom heat for about 25 minutes. Make a chopstick test. Let the cake cool down.
For the icing, sieve the powdered sugar and place in a small bowl. Mix with lemon juice to a firm icing and brush the cake with it.