Apply rub to tri tip at least 2 hours before grilling. Heat 3 or 4 burners of a gas grill on high for 10 minutes. Sear tri tip on fat side first with lid down for 2 or 3 minutes. Rotate 1/4 turn to get cross hatched grill marks on surface and leave for 2 more minutes. Flip tri tip over to bottom and sear for 5 minutes with lid down. Shut off burner on 1 side and move meat to the side that is turned off. Close lid of grill and let cook for approximately 30 minutes for a 2 1/2 to 3-pound tri tip. Test meat for doneness and apply the barbeque sauce for last 5 minutes of grilling. Slice thin and pile on buns with additional barbeque sauce.
Mix all ingredients except salt. Salt can be added to the meat before the rub but in proportion to the type of meat you are grilling.
Heat butter in a sauce pan until bubbly. Add onion and cook until softened. Add liquid smoke and Worcestershire sauce and cook 1 minute. Add the sugar, ketchup, black pepper, cayenne pepper and the dash of mustard. (The mustard will make the sauce very tangy, be careful not to add too much.) Mix and let simmer slowly for about 5 minutes. Add the lemon juice, to taste, to balance out the sugar. Mix and turn off flame. Sauce is ready to use.
A viewer or guest of the show, who may not be a professional cook, provided this recipe. It has not been tested for home use.