Wash and dry the lemons. Finely grate the zest of 1 lemon, peel the zest of the other lemon in fine strips or peel thinly and cut into strips. Halve the lemons and squeeze.
Wash apples, quarter them, remove seeds and cut them into thin slices. Immediately sprinkle with half the lemon juice. Peel ginger and grate finely.
Separate eggs. Mix egg yolk, 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 whites and 1 pinch of salt until stiff and fold in loosely.
Pour the curd mixture into a greased ovenproof mould. Dab apple slices dry if necessary and put them into the mixture. Bake in the preheated oven (electric oven: 200 °C/circulating air: 175 °C/gas: level 3) for 30-35 minutes.
Sprinkle the casserole with the remaining lemon peel.