Peel the vegetable onion and cut into slices. Clean, wash and cut the peppers into large cubes. Wash zucchini thoroughly, cut off ends. Peel the zucchini lengthwise into thin slices with a peeler.
Wash and halve the tomatoes. Peel garlic. Chop 2 garlic cloves finely. Peel onion and chop finely. Pour beans on a sieve, rinse with water and drain. Wash lemon thoroughly and cut into slices.
Wash mint, dab dry, pluck leaves from the stalks and cut into strips. Mix yoghurt, sour cream, lemon juice and mint. Season with salt, pepper, sugar and coriander. Heat 6 tablespoons of olive oil in a large casserole dish, fry onion slices, herbs, paprika and remaining garlic cloves in it while turning.
Add tomatoes, zucchini, beans and lemon and braise over medium heat for about 12 minutes. Then season to taste with salt, pepper and coriander. In the meantime, heat the remaining oil in a pot, sauté diced onion in it, add couscous, deglaze with stock, bring to the boil and let it swell at low heat for about 4 minutes.
In the meantime melt butter and stir it into the couscous with a fork. Arrange the vegetables on a plate. Add couscous extra. Serve garnished with fresh herbs as desired. Add yoghurt sauce extra.