Divide the butter into large pieces and beat in a mixing bowl with the whisk of the hand mixer until foamy. Add sugar, vanillin sugar and salt and stir until you have a creamy mixture. Separate the eggs. Stir the egg yolks into the fat-sugar mixture. Wash and dry lemons and grate the peel. Squeeze 1 lemon. Stir in quark, milk, semolina, lemon juice and zest.
Beat the egg white until stiff and carefully fold into the quark mixture. Put the dough into a greased springform pan (26 cm Ø) sprinkled with breadcrumbs and smooth it down. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: not suitable/ gas: level 3) for 45 minutes. If necessary, cover with parchment paper after 30 minutes of baking time. Let the cake cool down for about 10 minutes. Remove from the springform pan and allow to cool completely. Dust with icing sugar before serving