Wash the fish, dab dry and season with salt and pepper. Peel garlic and onion and chop finely. Heat 1 tablespoon of oil in a saucepan. Sauté the garlic and onion until translucent.
Add the tomatoes, bring to the boil, chop coarsely with a spatula and simmer for about 10 minutes. Heat 1 tablespoon of oil in a coated pan. Fry the fish for approx. 4 minutes on both sides.
Wash spring onions, halve lengthwise and cut into strips. Put about 4 teaspoons aside for garnishing. Fold the rest into the tomato sauce. Season the sauce with salt, pepper, lemon juice and sugar.
Arrange sauce and fish on preheated plates, garnish with remaining spring onions and lemon wedges. Ciabatta tastes good with it.