Knead the flour, 75 g sugar, 1 piece of vanilla sugar, salt, 1 egg and 125 g butter into a smooth dough. Cover and chill for about 30 minutes.
Line a greased springform pan with it and draw a 5 cm high edge. Prick the bottom several times. Spread the poppy seed baking on the dough.
Separate 2 eggs. Mix 75 g butter, lemon zest, 1 piece of vanilla sugar and 75 g sugar until creamy. Add 2 egg yolks and 2 eggs one after the other. Stir in the quark and pudding powder. Beat 2 egg whites until stiff and pour in 75 g of sugar. Fold into the cheese mixture. Spread on the poppy seeds.
Bake at 150 degrees fan-assisted / 175 degrees electric stove for about 1 hour. Leave to rest in the switched off oven for about 10 minutes. Let cool in the mold (preferably overnight).