Defrost the fish, wash, squeeze out excess moisture.
Cut the fish into slices.
Peel, wash onions, cut into cubes.
Peel, wash, cut carrots into thin strips (or grate on a coarse grater).
Preheat a frying pan, pour in vegetable oil. Put half the onion in hot oil. Simmer over medium heat, stirring occasionally, for 3-4 minutes. Refrigerate.
Soak white bread (or a bun) in water. I recommend cutting the crusts off the bread.
Skip fish fillets, fried onions with butter squeezed bun through a meat grinder.
Salt, pepper and mix the minced meat well (preferably beat well on a bowl).
Preheat a frying pan, pour in vegetable oil. Form cutlets with wet hands and put in hot oil. Fry over medium heat for 2-3 minutes on each side (until golden brown). Fold the finished cutlets into a cauldron. So fry all the cutlets.
Boil the kettle. Preheat a frying pan, pour in vegetable oil. Put the carrots and the remaining onions in the hot oil. Simmer over medium heat, stirring occasionally, for 2-3 minutes. Then add the tomato. Mix. Season with salt, pepper, add sugar, bay leaf. Pour boiling water over. Mix.
Pour cutlets with prepared gravy. Boil. Cover, reduce heat to low. Simmer for 10-15 minutes.
Lean sea fish cutlets in tomato sauce are ready. Both hot and cold are good. Serve with your favorite side dish.