Place flour, one egg, fat in flakes, two tablespoons of water and a pinch of salt in a mixing bowl and knead with the dough hooks of the hand mixer. Then work into a smooth dough with your hands.
Wrap in cling film and chill for about 30 minutes. Peel onions and cut into rings. Cut bacon into wafer-thin slices. Heat oil in a frying pan. Leave the bacon out. Add onions and fry for five minutes until transparent.
Season with salt and pepper. Roll out the dough on a lightly floured work surface until round (30 cm Ø). Place in a lightly greased quiche tin (26 cm Ø) and press the rim up slightly. Spread the onions and bacon evenly on top.
Grate cheese. Whisk three eggs and sour cream. Season with salt, pepper and nutmeg. Stir in half of the cheese and pour over the onions. Sprinkle the rest of the cheese on top. Cook in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 30 to 40 minutes.
Arrange the quiche on a plate and serve garnished with marjoram.