Mix the margarine, sugar, vanilla sugar and eggs together. Sift the flour and baking powder into it and whisk well. Put half of the dough in a greased baking pan and distribute evenly. Place the apple pieces on top and cover with the second half of the batter. Bake for 60 minutes.
Take the cake out of the mold and let it cool down.
For the icing, sieve powdered sugar into a cup, mix well with lemon juice and warm water and spread on the cold cake. Let the cake rest briefly.