Wash the peppers, splash them with water, and bake in the oven at 350 degrees F for 40 minutes together with the onion cut in half, one garlic clove, and the washed tomatoes. Turn occasionally so that they brown all over but take care they do not burn. When soft, remove from the oven and cover the oven dish with paper so they sweat. This makes them easier to peel. When cold, peel and cut the peppers into strips, reserving any juice they release. Cut the onion into strips. Peel the tomatoes and the garlic clove and crush them together.
Thinly slice the other garlic clove and fry until golden.
Remove from the heat and add the strips of pepper and onion, the crushed tomato and garlic and the vinegar and pepper juices. Season with salt and pepper. Add the sugar to counter the acidity of the tomato and the vinegar. Bring to a boil and remove.
This makes an excellent salad on its own or the ideal garnish either hot or cold, for fried eggs, fish, or meat. In some towns in La Mancha, a teaspoon of cumin is added.