Preheat oven to 350° F.
Sprinkle onions over the bottom of a large heavy Dutch oven. Place the meat on top of the onions, cover, and bake 1 1/2 hours, adding some stock if the pan juices begin to dry up.
Mix garlic, tomato sauce, brown sugar, paprika, mustard, rosemary, thyme, lemon juice, catsup, vinegar and Worcestershire sauce in a bowl. Pour the sauce over the meat, cover, and continue to bake, basting every 20 minutes, until the meat is tender, about 1 1/2 hours longer.
Remove the lid for the last 1/2 hour of cooking. Slice the meat and arrange on a serving platter. Spoon some sauce on the top and serve the remaining sauce on the side.
Servings: 4