Drain the cranberries on a sieve. Wash apples, quarter them, remove the core. Cut apples into long, thin slices. Wash the lemon with hot water, grate the peel thinly and squeeze the juice.
Drizzle apple slices with the lemon juice. To make the custard, whisk the eggs and sugar for approx. 5 minutes with the whisk of the hand mixer until very creamy. Add lemon zest, sour cream and pudding powder and stir into the mixture.
Place the contents of the dough bag in a bowl. Add 1/8 litre of lukewarm water and knead the ingredients with the dough hooks of the hand mixer until the dough separates from the rim of the bowl. Briefly knead the dough with your hands and roll out into a circle (approx. 24 cm Ø) on a floured work surface.
Place the dough on a baking tray lined with baking paper and pull up a small bead at the edge so that the frosting does not run down. Spread half of the frosting on the dough.
Put 2/3 of the cranberries and half of the apple slices on top. Spread the rest of the custard on the fruit. Bake the fruit pizza in the preheated oven (electric cooker: 200 °C/ gas: level 3) for 25-30 minutes.
In the meantime, bring the remaining apple slices to the boil in the apple juice and 1 tablespoon of lemon juice and steam for about 3 minutes at low heat. Add 2 tablespoons of poppy seeds and the remaining cranberries and warm up.
Dust fruit pizza with icing sugar. Serve immediately with the steamed fruit and sprinkled with the remaining poppy seeds.