Step 1

Preheat the oven to 350 degrees Fahrenheit (175 degrees Celsius).

Step 2

Rub both sides of the meat with salt, pepper, and if desired, mustard.

Step 3

Spread half of the onions over bottom of a shallow roasting pan. Place the brisket, fat-side up, in the pan and top with the remaining onions. Add a quarter cup of water. Bake, uncovered and basting occasionally, until the meat and onions begin to brown (about one hour).

Step 4

Add the remaining water and remaining ingredients. (The liquid should never reach more than halfway up the side of the meat.) Cover, reduce the heat to 300°F or place over a low flame, and cook until the meat is fork-tender and the thickest part of the brisket registers about 175°F on a meat thermometer (two to three hours; allow about one hour of cooking time per pound).

Step 5

Cover the brisket loosely with foil and let stand 20 minutes before carving. Slice the brisket diagonally against grain into slices about an eighth of an inch thick.