Preheat the oven to 180°C (approximately 350°F) on the convection setting. Line a baking sheet with parchment paper.
Separate the eggs and beat the yolks with the sugar, quark, lemon zest and melted butter. Beat the egg whites with the pinch of salt until stiff and fold into the quark mixture.
Rinse and peel the apples. Cut out the cores with an apple corer and cut the apples into thin slices. Coarsely chop the peanuts. Lay the puff pastry on the baking tray and cover with the quark mixture. Place the apple slices on top and sprinkle with the chopped peanuts. Dust with some cinnamon and bake for 15-25 minutes until golden brown.