Peel and finely chop the onion. Clean, wash and very finely dice the peppers. Wash parsley, shake dry, pluck off leaves and chop finely. Boil 250 l salted water with 1 tbsp. oil. Stir the couscous into the boiling salted water.
Take the pot off the stove. Cover the couscous and let it swell for about 5 minutes.
Heat 1-2 tablespoons of oil in a frying pan. Steam the peppers for about 2 minutes. Add onion and fry for 1-2 minutes. Remove from the heat. Mix yoghurt and tahini in a bowl. Season to taste with salt.
Rinse fish under cold running water and pat dry well with kitchen paper. Mix paprika powder, cumin, 1 tsp salt and 1 tsp pepper. Rub the fish with the spice mix all around. Heat clarified butter in a large pan.
Fry the fish on both sides at high heat for about 2 minutes.
Loosen the couscous with a fork. Mix with paprika-onion-mix and parsley. Season with salt, pepper, 1 pinch of sugar and lemon juice. Serve the couscous with fish and yoghurt tahin sauce.