Whip the sugar, vanilla sugar and eggs with the whisk of the hand mixer until very creamy. Stir curd and pudding powder until smooth. Fold in the egg mixture. Grease the oven pan (32x38 cm) and sprinkle with semolina.
Set aside 1 cup of curd mixture and pour the rest into the mould. Mix the poppy seed baking and the rest of the quark mixture and pour spoonfuls of blobs onto the surface. Use a knife to draw through the blobs and marble them slightly.
Bake in the preheated oven (electric cooker: 175 °C/ gas: level 2/ convection oven: 160 °C) for about 1 hour. Leave to cool on a grid. Cut cake into 24 pieces, dust with icing sugar and serve.