Preheat broiler to high.
Arrange the tomatoes and chiles on an aluminum foil-lined broiler pan skin side up. Broil until their skins start to char and shrivel, about 10 to 12 minutes or until they are soft. Transfer the tomatoes and the chiles to a blender, puree, and set aside.
Heat the olive oil in a medium saucepan over medium-high heat. Add the onions and the garlic and cook until soft, 2 to 3 minutes. Stir in the oregano, cumin and Worcestershire sauce. Add the tomato puree and simmer until the sauce is slightly thickened and the flavors have blended, 10 minutes. Season with salt.
Serve with various chips and vegetables.
Recipe courtesy of Ingrid Hoffmann, 2007