From Stacy Moses, I tried it and there was not a piece left!
1 package prepared good seasons dressing (Stacy says to use balsamic vinegar instead of red wine vinegar for this recipe)
2 onions, diced
4 tablespoons yellow mustard
3 - 4 pound brisket
Salt and pepper to taste
Prepare salad dressing mix according to directions, using balsamic vinegar in place of red wine vinegar.
Place brisket fat side up, lightly salt and pepper the top.
Spread mustard over salt and pepper (can use more mustard to cover brisket)
Pour prepared dressing over brisket and top with onions, add about a cup of water around brisket.
Cover the brisket well and bake at 350 until tender about 2 to 2½ hours.