Line a baking tray (approx. 35 x 40 cm) with baking paper. Separate the eggs. Beat the egg whites and 3 tbsp. cold water until stiff, adding 75 g sugar and 1 pinch of salt.
Preheat oven (electric cooker: 200°C/circulating air: 175°C/gas: level 3). Whisk the egg yolks with a fork and fold into the beaten egg white. Sieve flour, starch and baking powder onto the egg mixture and fold in.
Immediately spread the sponge cake mixture on the baking paper until smooth. Bake in a hot oven for about 10 minutes until light. Sprinkle 4-5 tablespoons of sugar evenly on a clean tea towel.
Carefully turn the hot sponge cake plate over onto the cloth. Immediately moisten and remove the baking paper, otherwise it will stick.
Roll up the sponge cake with the cloth from one long side and let it cool down. Mix quark, 100 g sugar, vanilla sugar, lemon peel and juice. Whip the cream until stiff and allow the cream setting agent to trickle in.
Lift under the quark.
Unroll the sponge cake. Spread lemon cream on top, leaving a rim of about 2 cm all around. Lift the cloth on one long side and use it to roll up the sponge cake again. Chill for at least 4 hours.
Dust with icing sugar.