Peel, wash and quarter the potatoes. Cover and cook in little salted water for about 20 minutes
Peel and chop the onion and garlic. Sauté both in a coated pan in hot oil. Add the tomatoes. Season with salt, pepper and sugar. Bring to the boil and simmer covered for about 10 minutes
Wash the fish and pat dry. Sprinkle with lemon juice. Season with salt and pepper
Stir the peas into the tomato sauce. Put the fish on top and let it simmer covered for about 8 minutes. Drain the potatoes. Arrange everything and garnish