Quickly make a smooth dough from the ingredients for the shortcrust pastry, roll out in a 28 cm springform pan, prick with a fork and place in the refrigerator for at least half an hour.
Preheat oven to 180 ° O / U. After half an hour, take the mold out of the refrigerator and prebake the shortcrust pastry for 10 minutes.
In the meantime, use the ingredients for the batter to make a smooth dough. Heat the first 4 ingredients for the filling in a coated pan and reduce to a caramel. When the mixture becomes thick, stir in the walnuts. Immediately spread this mixture onto the pre-baked shortcrust pastry. Spread the apple halves on top with the curvature facing up. Now pour the batter over it, place in the oven for 45-50 minutes and finish baking (chopsticks test). Let the cake cool down, remove it from the mold and cover with powdered sugar.