Grease a springform pan (26 cm Ø) and dust with flour. Wash lemon hot, dab dry. Finely grate the peel. Squeeze lemon. Knead 250 g flour, 75 g sugar, 1 pinch of salt, half lemon zest, 1 egg and 125 g butter in pieces first with the dough hooks of the mixer, then briefly with your hands to a smooth shortcrust pastry.
Roll out on some flour round (about 32 cm Ø). Place in the form, pressing up the edge by about 4 cm. Prick the bottom several times with a fork. Chill for about 1 hour.
Finely grind 50 g almonds. Bring milk to the boil and remove from the stove. Stir in poppy seeds, 75 g sugar, vanilla sugar, bitter almond flavour and ground almonds. Let it cool down for about 10 minutes, then stir in 2 eggs.
Let it cool down.
Mix ricotta, sour cream, 100 g sugar, lemon juice, the rest of the lemon peel and 4 eggs. Sift the starch on top and stir in. Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: manufacturer).
Spread the poppy seed mixture on the dough base until smooth. Spread the ricotta cream on top. Bake in a hot oven on the lowest shelf for 55-60 minutes.
Wash, halve and stone the apricots. Cut into wide slices. Remove cake from the oven. Spread the apricots on top. Sprinkle the rest with almonds. Bake at the same temperature on the middle shelf for 25-30 minutes.
Heat up jam and 1-2 tablespoons of water. Take out the cake, spread with jam immediately. Let cool off. Carefully remove from the mould.