Cut the fish in portions.
Mix crackers with pepper and salt. Roll the fish in this mixture and fry in vegetable oil until golden brown.
Pull the fish into a plate, and in the same pan, fry the chopped onion until soft, then add the tomato, sugar, peppercorns, bay leaf, salt and pepper to taste. Cook for 5 minutes.
Then put the fish in the tomato and cook over low heat under the lid for 10 minutes.