2. Toss the whole tomatoes and onions with 1 tablespoon of olive oil and a pinch or two of salt and spread them out on a baking sheet.
3. Roast them on the top rack of the oven until they are very soft and their juices are bubbling, about an hour. Remove from the oven, cool and turn the oven up to 350°F.
4. When the tomatoes and shallots are cool enough to handle, remove and discard their skins.
5. Roughly chop the tomatoes and onions. Mix the tomato mixture, chili, bay leaf and oregano together in a shallow baking dish. Season with salt and pepper and sprinkle with olive oil and balsamic vinegar.
6. Bake, uncovered, stirring occasionally to prevent the edges from browning. Cook until the juices have evaporated, about 30 minutes. This can be made in advance and stored in the refrigerator for up to 1 week. Serve this as an accompaniment to grilled meats and fish, especially in Southwestern dishes.