Grease a tart mould (approx. 28 cm Ø) with a removable base. Separate 1 egg and chill the egg white. Knead 250 g flour, 125 g sugar, vanilla sugar, salt, 150 g butter in pieces and 1 egg yolk.
Roll out the dough on a little flour to a circle (approx. 32 cm Ø), place it in the form, press down the rim and base. Prick the base several times with a fork. Cover and chill for about 40 minutes.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2). For the compote, peel, quarter, core and cut apples into small cubes. Stir 5 tbsp. apple juice and pudding powder until smooth. Remaining apple juice, 5
Stir in the pudding powder, bring to the boil and simmer for about 1 minute, stirring continuously. Let it cool down a little bit, stirring more often.
For the poppy seed mixture, mix 1 egg white, 3 eggs and the poppy seed filling. Sprinkle the dough base with breadcrumbs. Smooth the apple compote on top. Spread the poppy seed mixture on top as well. Bake in the hot oven on the lower shelf for about 35 minutes.
For the meringue, beat 3 egg whites until stiff, adding 125 g sugar. Take the cake out of the oven, spread the beaten egg whites evenly on top and bake at the same temperature for another 20-25 minutes.
If necessary, cover with aluminium foil about 15 minutes before the end of the baking time. Let it cool down and dust with icing sugar.