2 tablespoons olive oil
2 tablespoons jalapeño chiles, seeded/minced
1/2 cup onion, chopped
2 cups tomatoes, chopped
2 teaspoons vinegar
1/4 teaspoon ground black pepper
Light beef broth or water
Heat olive oil, then add chiles and onion; cook until they begin to soften, but do not allow them to brown. Add remaining ingredients except for water or broth and cook, stirring frequently, for 1/2 hour over very low heat.
Add just enough broth or water to make the sauce a little soupy and continue cooking an additional 10 minutes. The sauce should be thick enough to coat a spoon without immediately running off, so add more liquid or cook a while longer, as necessary.
Yields enough to serve 4 with chips or with a meal.