Chipotle Sauce Toss the tomatoes in vegetable oil and preferably grill the onions and the toma toes, over Mesquite coals. The tomatoes should have charred skins (if not grill ing, char tomatoes skins in a very hot skillet and then add the onions with som e vegetable oil to a hot sauce pan) Add garlic and continue to cook for about 2 mins. Add the oregano, cilantro, and the chilies, which have been rinsed and c leaned of their veins, and seeds and cook slowly, covered, for about 20 minutes . Let cool and then puree in the blender, adding the lime juice and salt and pe pper to taste. For spicier sauce, add some of the adobo from the canned chilies .