Preheat oven to 350 degrees. Place brisket in a roasting pan and brush with liquid smoke. Combine the salt and spices in a small bowl, mix well. Apply this on the brisket with a brush. Cover the roasting pan and bake until the brisket is fork tender, about 3 hours. Remove the pan from the oven and use two forks to pull the meat apart, shredding if coarsely. For each sandwich, halve a roll. Spoon 2 tablespoons heated barbecue sauce over the bottom. Using a slotted spoon, pile about 1 cup of the shredded meat on each roll. Pour 2 or 3 tablespoons sauce over the meat and cover with the top half of the roll. Serve with additional Barbecue Sauce on the side. Barbecue Sauce: Heat the oil in a medium sized pan. Add the onion, garlic, cumin and cayenne and saute' at 200ºC or 5 minutes or until the onions are light brown. Stir in the remaining ingredients and simmer, stirring, until slightly thickened, about 10 minutes. Makes 2 cups.