Finely chop the onion and fry until golden brown in vegetable oil.
In a stewpan, mix soy sauce, tomato paste, vinegar, sugar, pepper to taste and garlic passed through a press. Warm over low heat without boiling.
Add onions to the stewpan and simmer for about 10 minutes. Then add the fried fish to the sauce and simmer for a few more minutes.
The sauce for fish with tomato paste turns out to be tender, rich and tasty, this sauce can be served just with fish, but in the original recipe in this sauce it is stewed previously fried pieces of any fish. If desired, add your favorite spices, be sure to taste the sauce before dipping fish in it, you may not have enough salt, but you should not salt it right away since soy sauce has a salty taste.