Wash and peel the apples and prick out the core. Cut apples into slices and sprinkle with lemon juice. Cream fat, 150 g sugar, salt and lemon peel. Stir in 3 eggs one after the other. Mix flour and baking powder and stir in briefly together with the milk. Pour the dough into a greased springform pan (26 cm Ø) sprinkled with breadcrumbs and smooth it down (if necessary, spread a little higher at the edges than in the middle).
Mix sour cream, remaining eggs, remaining sugar and vanilla sugar. Pour half of it on the dough and cover it in a circle with the apple slices. Pour the rest of the custard over the apple slices and bake in the preheated oven (electric range: 175 °C/ gas: level 2) for about 1 hour. Heat up the apricot jam and pass through a sieve. Spread apple slices with jam thinly and let the cake cool down. Dust the edges of the cake with icing sugar