1. Preheat oven to 400 degrees F.
2. Prepare brisket. Place onions, garlic, and water in a large (6-quart) Dutch oven or stockpot. Rub salt, paprika, and pepper all over brisket, then place meat on top of onions. Pour tomatoes over meat. Cover pot with a tight-fitting lid or two layers of foil and place in oven. Cook for 15 minutes. Reduce heat to 325 degrees F and cook for 2 3/4 to 3 hours or until a kitchen fork easily pierces the meat. (Brisket can be made up to three days ahead.
3. Cool uncovered; then cover and refrigerate. Cooked brisket can be frozen, wrapped tightly in plastic wrap and an outer layer of foil, for up to a month.)
4. Transfer meat to a plate. Spoon fat from surface of braising liquid. (If meat has been refrigerated, it's easy to skim off congealed fat.) Reserve 1 1/3 cups of braising liquid and discard the rest.
5. In the same pot, prepare barbecue sauce. Combine 1 1/3 cups of reserved braising liquid or tomato sauce, ketchup, molasses, vinegar, onion powder, garlic powder, cinnamon, allspice, and cayenne pepper. Bring sauce to a boil. Lower heat and simmer, stirring occasionally, for 20 minutes or until flavors are blended. Taste for seasoning. (Sauce can be made ahead; reheat before serving.)
6. Preheat grill to medium. Have brisket at room temperature. Grill brisket at room temperature. Grill brisket for 5 to 10 minutes per side or until heated through and lightly charred. Transfer brisket to a cutting board and slice it across the grain into thin slices. Place brisket on a platter and spoon some of the barbecue sauce over it. Serve remaining sauce in a separate bowl.
Source: Hannaford fresh Magazine, July - August 2008