For the dough, stir the sugar, flour, eggs and baking powder until foamy, add cinnamon if necessary, and pour into a greased springform pan sprinkled with breadcrumbs.
Peel the apples, cut into thin wedges and spread on the dough. Press something down. The shape can be filled to the edge.
For the topping, dissolve the butter in a saucepan and add the sugar. Roughly chop the walnuts and spread them over the apples. Now distribute the butter and sugar over the apples.