Peel and dice the apples, sauté briefly with the lemon juice. After cooling, mix in the melted butter, almonds and sugar.
Prepare a batter from the other ingredients (with the zest of the lemon). Put 3/4 of it in the greased springform pan sprinkled with oat flakes. Spread the filling on top. Place the rest of the dough on top of the filling in small piles.
Bake at 170 ° C for a good hour on the lowest rack.