Whisk mascarpone, sugar and calvados until its smooth and chill it in the fridge.
Preheat the oven to 170°C. Grease a springform pan (16 cm) slightly with butter and line with parchment paper (bottom and edges).
Remove apple seeds with seeder and cut it into slices. Melt down butter in a small pan and pour it on the bottom of the baking pan. Dust even with 2 – 3 tps sugar and lay down the apple slices all-over the bottom.
Separate egg whites from egg yolks. Whisk egg whites until you have stiff peaks. Whisk remaining sugar, oil and egg yolks. In another bowl mix almond, flour, polenta, baking powder, lemon zest and salt and pour it to the oil mixture combine very well. Mix in the yoghurt. Finally fold in the egg whites. Pour dough carefully over the apple slices and bake for 45 – 50 minutes (depending on your oven). After baking let the cake cool down in the pan for 15 minutes than turn out of the baking pan (upside down) and let cool down on a wire rack.
When the cake is completely chilled. Cut the cake and fill it with mascarpone cream.