Bring the milk with the poppy seeds to the boil and allow to cool. In the meantime, peel and quarter the apples, remove the core and cut the quarters into small cubes.
Mix the butter with sugar and marzipan until foamy, gradually stir in the eggs, stir in the lemon juice, vanilla, salt and the milk and poppy seed mixture. Mix the flour and baking powder and stir in briefly. Fold the apple cubes into the batter.
Pour the dough into the greased and floured deep baking sheet. Bake at top / bottom heat 180 ° C, hot air 160 ° C for about 45 minutes, then leave to cool.
For the icing, mix powdered sugar with lemon juice to a thick mass, remove 1 tablespoon of it and spread the icing on the cake. Stir in the retained tablespoons of icing cocoa and possibly a little more water, put in a freezer bag, cut off a small corner and squirt strips onto the icing.
The cake can be prepared the day before. Instead of icing sugar, a couverture coating also tastes very good.