1. Combine shallots, garlic, chili powder, paprika, cinnamon, oregano and salt in a small bowl. Rub into both sides of meat. Set the meat in a 9-by-13-inch baking dish, cover and refrigerate for at least 8 hours or overnight. 

2. Pour Worcestershire sauce over the meat. Cover the pan with foil and set aside at room temperature while the oven heats to 350°F.Bake the brisket, covered, for 2 hours. Meanwhile, blend tomatoes, brown sugar and vinegar in a large blender or food processor until smooth. 

3. After 2 hours, pour the tomato mixture over the meat; continue baking, covered, until fork-tender, basting with pan juices every 30 minutes, for about 1 1/2 hours more. 

4. Remove the meat from the sauce. Let rest for 10 minutes, then slice against the grain. Skim the fat from the sauce in the pan; pour the sauce over the meat and serve (or follow make-ahead instructions).