Mix 3 cups yogurt, 250g quark, 120g sugar, 2 egg yolks, and juice of half a lemon in a bowl. Stir in 400g frozen blueberries. Pour into an ovenproof glass bowl and refrigerate for at least 3 hours until cold.
Beat 3 egg whites and 150g sugar until very stiff peaks form.
Remove the yogurt mixture from the refrigerator. Using a tablespoon, place large spoonfuls of the meringue on top. Bake in a preheated oven at 120 to 150°C (250 to 300°F) until the tips turn light brown, about 20 to 30 minutes.
Serve immediately while the meringue is warm and the yogurt mixture is cold.