1. Mix the flour and salt for the dough in a large bowl. Add the butter in small pieces and rub everything between your fingers until you get different-sized streusels. Add the egg and water and knead until a smooth dough forms. Wrap in plastic wrap and place in the fridge for at least 30 minutes.

2. While the dough is resting, peel the onions and cut them into thin rings. Cut the bacon into small dice. Heat some oil in a nonstick frying pan and fry the bacon for some time. Add the onions and fry them until soft and glossy. Season with salt and pepper. Set aside.

3. Preheat the oven to 200°C (390˚F). Roll out the dough on a lightly floured surface. Grease a 26cm quiche tin with a loose bottom* and transfer the dough to the tin and press it to the bottom and sides. Cut off overlapping dough. Transfer the onions and bacon to the tin and spread evenly. Sprinkle some caraway seeds on top (optional).

4. Mix the eggs with the sour cream and season well with salt, pepper, as well as some freshly grated nutmeg. Add half of the grated cheese and mix it in. Pour the mixture over the onions and sprinkle the remaining cheese on top. Bake the onion quiche for about 30-40 minutes – the filling should have set and the top look golden brown. Take it out of the oven and let it cool down for a moment. Remove from the tin and serve warm.