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, ketchup, 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.