1Trim excess fat from brisket and place fat side up in a roasting pan.
2Sprinkle with salt, pepper and garlic.
3Place onion slices over meat.
4Bake, uncovered, at 350 for 1 1/2 hours.
5Combine 1 1/2 cups water, tomato sauce, and next 8 ingredients; pour over brisket.
6Cover with aluminum foil and bake 2 hours or until tender, spooning sauce over brisket occasionally.
7Transfer brisket to serving platter and pan juices to a saucepan.
8Combine cornstarch and remaining 1/2 cup water.
9Gradually add to pan juices, stirring constantly.
10Bring to a boil; boil 1 minute, stirring constantly.