For the sauce, place the tomatoes on the unheated rack of a broiler pan. Broil 3 to 4 inches from the heat for 12 to 14 minutes or until the tomato skins are blistered and begin to blacken, turning occasionally. Transfer tomatoes to a mixing bowl. Cool. Coarsely chop (tomatoes will be soft-do no peel). Set aside.
Wearing rubber or plastic gloves, seed stem, and finely snip or crumble the pasilla pepper. Set aside.
In a heavy medium saucepan melt 2 tablespoons butter over medium heat; add the onion and cook about 5 minutes or until lightly browned. Add the sweet pepper and garlic. Cook about 4 minutes or until tender. Stir in the red wine vinegar and dry white wine. Bring to boiling, scraping up any browned bits; reduce heat. Simmer, uncovered, about 5 minutes or until liquid is reduced to half of its original volume. Stir in tomatoes, pasilla pepper, and chicken broth. Bring to boiling; reduce heat. Simmer, uncovered, about 15 minutes or until mixture is reduced to 2-2/3 cups.
Pour half of the mixture into a blender container or food processor bowl. Cover and blend or process until nearly smooth. Pour into a bowl. Repeat with remaining mixture. Stir in oregano and thyme, Of desired, cover and refrigerate until serving time.
Trim any fat from the steaks. Season the steaks with salt and pepper. Grill the steaks on the rack of an uncovered grill directly over medium coals to desired doneness, turning once. (Allow 8 to 12 minutes for medium-rare doneness.)
Before serving, bring the sauce to a simmer; heat through. Remove saucepan from the heat. Whisk in the remaining 2 tablespoons butter. Season sauce with salt and pepper. Place the steaks on serving plates. Serve sauce with the steaks. Makes 6 servings.