Place puff pastry sheets next to each other and allow to thaw. In the meantime peel, quarter, core and cut apples into slices. Bring sugar, lemon juice and cider to the boil in a large pan. Steam the apple slices for about 5 minutes. Remove from the pan and let cool and drain. Place the puff pastry slices on top of each other and roll out on a lightly floured work surface. Cut out a circle (30 cm Ø).
Grease a pizza form (26 cm Ø) and sprinkle with semolina. Pour in the dough, pressing the rim up a little. Prick the base several times with a fork. Put apple slices into the form. Mix sour cream, eggs, icing sugar, lemon peel and vanilla sugar. Pour over the apples. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) on the lower shelf for approx. 30 minutes