Line the troughs of a muffin tray (twelve troughs) with one paper baking tin each. Preheat the oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Wash lemon hot, dry and finely grate the peel.
Halve the lemon and squeeze 1 half.
Whisk the eggs, sugar and vanilla sugar with the whisk of the mixer for approx. 4 minutes until thick and creamy. Briefly stir in oil, sour cream, lemon peel and lemon juice. Mix flour and baking powder, sieve over it and stir in briefly.
Spread the dough into the paper cups. Bake in a hot oven for about 25 minutes.
Remove the muffin tray from the oven and lift the muffins out of the troughs. Let them cool down on a cake rack. If necessary, sort out blueberries, wash and drain. Dust the muffins with icing sugar and decorate with blueberries.