A lot of Texans eat their barbecue without a sauce, or with just meat juices laced with cayenne, but others prefer a robust sauce full of Southwestern seasonings.
In a saucepan, warm the oil over medium heat. Add the onions, jalapeños, serranos, and garlic and sauté over medium heat until everything is softened. Mix in the remaining ingredients and bring the sauce to a simmer. Cover and cook for 35 to 40 minutes. Allow the sauce to cool briefly.
Strain the sauce and puree the solids in a food processor. Return the pureed