Put the margarine in a mixing bowl and stir until creamy, then add the sugar and vanilla sugar. Add the flour and the packet of baking powder and stir vigorously, now add one egg after the other to the dough, stir thoroughly after each egg. Finally add the lemon aroma and 1 teaspoon lemon pulp and stir in well.
Grease a cake tin and pour the batter into it. Bake at 175 ° C (top / bottom heat) for 55 minutes. When the cake is still warm, brush all over with lemon juice using a baking brush.
For the topping, stir together the remaining lemon juice and powdered sugar until the mixture is nice and creamy and free of lumps. Spread the icing on the cooled cake.