In a saucepan, heat 4 tablespoons olive oil and fry the finely chopped onion and 2-3 cloves of garlic. Add 5 cups (1.2 L) vegetable broth, cover and allow it to boil for 5 minutes. Then add 2 potatoes, 2 sliced and chopped red bell peppers.
Stew for about 7 minutes, add the fish and 1 peeled and finely chopped tomato. Simmer for another 7 minutes. Add salt and pepper, and finally add chopped parsley, too.