Mix flour and salt. Add 1 egg. Warm milk lukewarm, dissolve yeast and butter in it, pour on the flour and knead with the dough hooks of the hand mixer to a smooth dough. Cover the dough and let it rise in a warm place for about 40 minutes. In the meantime peel and roughly dice the onion. Clean, wash and slice the zucchini.
Clean, wash and halve the tomatoes. Heat the oil in a large frying pan, fry the onion and courgette for about 5 minutes at medium heat, turning them over. Season with salt and pepper. Remove from the pan and let it cool down. Press the dough with well floured hands into a greased tart tin (28 cm Ø), pressing the rim slightly up. Let it rise again in a warm place for about 15 minutes. In the meantime wash parsley, dab dry and chop finely, except for a little bit for garnishing. Mix the sour cream and the remaining eggs. Season with salt and pepper and stir in parsley. Mix zucchini and onion pan, tomatoes and peas. Spread the vegetables on the dough.
Let it rise again in a warm place for about 15 minutes. In the meantime wash parsley, dab dry and chop finely, except for a little bit for garnishing. Mix the sour cream and the remaining eggs. Season with salt and pepper and stir in parsley. Mix zucchini and onion pan, tomatoes and peas. Spread the vegetables on the dough. Pour egg custard over the mixture and bake in a preheated oven (electric range: 200 °C/ gas: level 3) for 30-35 minutes. Serve garnished with parsley as desired