Drain the apricots in a sieve. Separate the eggs. Cream egg yolk and oil. Stir in 100 g icing sugar, vanillin sugar, lemon zest, salt and soured milk. Beat the egg whites until stiff, while pouring in 50 g icing sugar. Mix flour, starch and baking powder. Alternately fold the egg white and flour into the soured milk mixture.
Line 1 muffin tin (12 wells) with paper cups. Spread the dough evenly over them. Place 1 apricot half on top with the convex side facing upwards. Use the remaining apricots for other purposes. Bake the muffins in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for 20 minutes. Remove from the oven and let them cool down on a cake rack. Dust the muffins with icing sugar