Wash the lemon and dry. Finely grate the zest of 1 lemon, peel the zest of the other lemon in strips or peel it thinly and cut it into strips. Halve the lemons and squeeze.
Wash apples, grate dry, quarter, core and cut into slices. Immediately sprinkle with half the lemon juice. Peel ginger and grate finely. Separate eggs. Mix egg yolks, honey, butter and 1 pinch of cocoa until creamy.
Stir in ginger, grated lemon peel and the rest of the juice. Then stir in semolina and quark. Beat egg white and 1 pinch of salt until stiff and fold in loosely. Pour the quark mixture into a greased ovenproof dish.
Dab apple slices dry if necessary and put them into the mixture. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 30-35 minutes. Sprinkle casserole with remaining lemon peel.