Preheat the oven to 180 degrees top / bottom heat.
Separate 3 eggs. Beat 3 egg whites until stiff. Mix the egg yolks with the quark, semolina, egg white powder, baking powder, stevia, flavedrops and (if desired) some cinnamon well.
Chop 1 peeled apple and the banana and carefully fold them into the rest of the mixture together with the egg whites.
Put everything in a casserole dish and peel the second apple and cut into thin slices, cover the casserole with the apple slices and sprinkle with a little cinnamon if necessary. Bake for 50 - 60 minutes and ideally enjoy while still warm.