Preheat the oven to 175 ° C. Grease a springform pan (26 cm). Knead the flour, butter, sugar, egg yolk and salt into a shortcrust pastry and use it to line the mold. Pull up a small edge and refrigerate the mold for 30 minutes. Separate the eggs. Beat the egg whites until stiff. Whisk the ricotta with egg yolks, sour cream, sugar, vanilla sugar, grated lemon zest and starch. Season to taste with lemon juice and fold in the egg whites. Drain the Amarena cherries well and spread them on the shortcrust pastry base. Gently spread the ricotta cream on top. Bake the cake on the 2nd rack from the bottom for about an hour. Then leave to cool for 30 minutes in the switched-off oven. Heat the apricot jam, strain it through a sieve and brush the surface of the cake with it. Lightly brown the flaked almonds in a pan without fat and sprinkle them on the cake.