How to make
In a bowl, cut the cold butter into thin slices and add the flour, sugar, grated lemon rind, baking powder, yoghurt and egg yolks, knead a smooth dough.
Divide the dough into 2 equal parts, wrap them separately in plastic wrap and put them in the fridge for 2 hours.
In the meantime, make the filling. Start by cutting the peeled apples into thin slices.
Put them in a pot, pour on the lemon juice, add the sugar, vanilla and stir carefully. Put the pot on the stove and saute the filling on low heat for about 5 min.
Take the pot off the heat, add the raisins and cinnamon and stir carefully.
Heat the oven to 360°F (180 °C). Lay out a rectangular oven dish with baking paper, lay out 1 part of the dough in it like a sheet, put the oven dish in the oven and bake 10 min. until semi-cooked.
Smear it with the jam and sprinkle with 1/2 the walnuts. On top, distribute the cooled apple filling evenly and sprinkle the remaining walnuts on.
Using a grater, grate the other dough part evenly on top. Put the oven dish in the oven again and finish baking for about another 40 min.
Take the baked cake out, put it with the baking paper on a cooking grid to cool fully. Cut it into squares and sprinkle generously with powdered sugar.
