Thaw the puff pastry.
For the filling: Separate the eggs. Rinse the lemon under hot water, pat dry, finely grate the zest and squeeze the juice. Whisk the egg yolks, quark, sugar, vanilla sugar, raisins, apricots, lemon juice and lemon zest together. Whip the egg whites until stiff and fold in.
Roll out the puff pastry on a lightly floured work surface to about 30 x 30 cm (approximately 12 x 12 inches). Spread the filling over the dough, leaving a narrow border free then roll up. Place on a baking sheet lined with parchment paper, brush with melted butter and bake in a preheated oven (175°C) (approximately 350°F) for about 35-40 minutes. Let cool slightly and serve warm or cold.