Knead the flour, salt, butter, 1 egg and 2 tablespoons of cold water into a smooth dough. Cover and chill for about 30 minutes. Peel onions and cut into rings. Fry bacon in a hot pan until crispy. Add onion and fry until transparent.
Remove pan from heat. Wash parsley, dab dry, cut into fine strips, put something aside for garnishing. Mix the rest with 4 eggs, cream and cheese. Season to taste with pepper. Roll out the dough rectangularly (approx. 24 x 32 cm) on a floured work surface. Grease a rectangular tart tin (20 x 28 cm) and line with the dough. Cut off any protruding edges. Spread the bacon-onion mixture in the tin. Pour egg cream over it.
Grease a rectangular tart tin (20 x 28 cm) and line with the dough. Cut off any protruding edges. Spread the bacon-onion mixture in the tin. Pour egg cream over it. Bake in the preheated oven (electric range: 200°C/ convection oven: 175°C/ gas: level 3) on the lower rack for 35-40 minutes. Sprinkle with parsley