Zwiebelkuchen German Onion Tart

Zwiebelkuchen, which literally means "onion cake" in the German language, is actually a savoury tart (a quiche?) prepared with onions and sour cream on a leavened or yeast dough, that is very popular in the German wine-growing regions. Serve them warm with a glass of chilled half dry German Risling or fruity Corbières if you prefer red.
Quark Dough adapted from Grundrezept Quark-Öl-Teig
Topping Recipe adapted from Tobiaskocht

Topping	Quark Dough
4 Yellow onions 3 stalk Spring onions 2 tbsp Olive oil 200 g Herb crème fraîche Salt and pepper to taste 1 tsp Cumin seeds	350 g All purpose flour 15 g Baking powder 1/3 tsp Salt 50 g Sugar 1 Egg, small 220 g Quark, lean (Magerquark) ©angiesrecipes 80 g Olive oil 80 g Milk

1. Cut the ends off the onions and slice them into thick rings. Slice the spring onions into rings too. Heat a skillet with olive oil over medium flame. Add in onions and stir-fry until lightly golden. Stir in chopped spring onions. Season the mixture with salt and pepper. Turn off the heat and set aside.
2. Combine the flour, baking powder, salt and sugar in a mixing bowl. Add in egg, Quark, olive oil and milk. Stir until the dough forms a ball. Preheat the oven to 180C/350F. Line a baking tray, about 30x40 cm, with parchment paper. Roll out dough on a lightly floured surface into a rectangle and fit into prepared baking tray.
3. Top the dough with the herb cream evenly. Spread the caramelized onion all over the cream. Sprinkle the top with salt, pepper and cumin. Bake for 25-30 minutes until beautifully browned.