Washing apples. Remove the core with an apple corer. Cut apples crosswise into slices. Sprinkle with lemon juice.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Grease a springform pan (20 cm Ø) and dust with flour. Cream 200 g butter, sugar, cinnamon and 1 pinch of salt with the whisks of the mixer.
Stir in the eggs one by one. Mix 200 g flour and baking powder. Stir into the butter-sugar cream. Spread half of the apple slices in the form. Pour the dough on top. Cover with the rest of the apple slices. Chop hazelnuts coarsely and sprinkle over the cake.
Bake in a hot oven for 40-45 minutes.
Stir the jam until smooth. Remove the cake. Spread with jam immediately, let cool down. Whipped cream tastes good with it.