Process all the dough ingredients into a smooth dough and place in a greased springform pan. Peel, quarter and core the apples, score on the back and drizzle with the lemon juice. Distribute the apple quarters on the dough and press lightly. Bake in the preheated oven with top and bottom heat at 175 ° C for approx. 30 minutes.
For the brittle, caramelize the sugar in a saucepan. Then stir in the butter and remove from the heat. Deglaze everything with the juice and always stir well, then add the walnuts. Spread on the cake immediately and bake for another 10 minutes.
Let the cake cool down and remove it from the mold - dust with powdered sugar and serve with cream.