Knead the flour, margarine, eggs and salt into a smooth dough. Shape the dough into a ball, wrap it in cling film and let it rest in the refrigerator for about 30 minutes.
Then roll out on a floured work surface and line a rectangular baking dish (20 x 30 cm) with it.
Preheat the oven to 200 degrees (convection 180 degrees).
Drain the feta cubes. Quarter or halve the tomatoes depending on their size.
Mix the sour cream, eggs and tomato paste together well and season with salt, pepper and, if you like, garlic. Distribute the icing evenly on the dough and top with the tomatoes and feta cubes.
Bake the quiche in the oven on the lowest rack for 35 to 40 minutes. If you want, you can garnish with rocket just before serving.