Wash, quarter and stone the apricots. Cream fat, sugar, vanilla sugar, lemon peel and eggs with the whisk of the hand mixer. Stir in buttermilk. Mix flour, salt, starch and baking powder and stir into the egg-sugar mixture in portions.
Wash blueberries, dab dry. Put the dough on the greased fat pan of the oven (36 x 41 cm; 3.5 cm deep) and smooth it down. Spread the apricots and blueberries on top and press in.
Bake in the preheated oven (electric cooker: 175 °C/ circulating air: 150 °C/ gas: see manufacturer) for 25-30 minutes (stick test). Remove the cake from the oven and let it cool down.