Heat the oil in a heavy-bottomed cast iron or stainless steel saucepan. Add the onions and garlic, toss until coated, cover and sweat on a gentle heat until soft but not colored. It is vital for the success of this dish that the onions are completely soft before the tomatoes are added. Slice the peeled tomatoes and add with all the juice to the onions and garlic.

Season with salt, freshly ground pepper, and sugar (canned tomatoes need lots of sugar because of their high acidity). Add the herbs. Cook, covered, for 10 minutes. Remove the lid and continue to cook for about 10 minutes more, or until the tomato softens. Cook fresh tomatoes for a shorter time to preserve the lively fresh flavor. Canned tomatoes need to be cooked for longer depending on whether you want to use the fondue as a vegetable, sauce, or filling.

Add a few drops of balsamic vinegar at the end of cooking to greatly enhance the flavor.

Variations

Add 1-2 chopped fresh chiles to the cooking onions.

Substitute 2-3 tablespoons chopped cilantro for the other herbs in the recipe. Good with or without chiles.