Eel in the Comacchio way

Preparation:

Preparation: Clean the eel with the ashes placed on strong fishmonger paper. If this is not possible, deprive it of the innards, wash it and cut it into pieces. Make 1 chopped onion and garlic and fry it in oil. Sprinkle with vinegar, let it evaporate and add the tomato sauce diluted in a little warm water to obtain a 2-inch gravy. Add salt and pepper. After 15 minutes, add the eel and cook over low heat for 30 minutes without stirring. Serve it with toasted polenta.