For this brisket, you’ll need a very large (about 12-inch) heavy skillet or Dutch oven so the meat has enough, or almost enough, room to lie flat. The meat will shrink as it cooks, so don’t worry if it rides up the sides initially. 
If desired, you can add 4 to 8 ounces of sliced mushrooms and 2 or more medium peeled russet potatoes, cut into large chunks. You can also peel 2 large carrots and cut them into coins. The mushrooms and carrots go in with all the ingredients; the potatoes go in after the first hour. The sauce cooks the potatoes during the second hour; if you put them in at the beginning, they get mushy. The potatoes should be done after an hour but can cook further once you take the meat out, if necessary. 
You can make this a day or two ahead; put it in the fridge and reheat later. This step allows you to skim the congealed fat from the top of the sauce. -- Betty Gordon 

Note: For Rosh Hashana and other holidays, dietary restrictions for Passover need not be observed as noted below. Regular ketchup and vinegar may be used. 

Hands on time: 20 minutes  Total time: 3 hours and 30 minutes  Serves: 6

Ingredients:

1 (3-pound) single brisket 
2 onions, sliced 
1 clove minced garlic 
1 cup kosher for Passover ketchup 
1 cup water 
3/4 cup brown sugar 
1/2 cup kosher for Passover vinegar 
1 teaspoon salt or to taste 
Freshly ground black pepper

Instructions:

Trim excess fat and pierce brisket all over on both sides with a fork. 
In a very large, heavy skillet or Dutch oven with a lid, over medium-high heat brown the brisket on all sides. Remove to a plate and set aside. In same skillet, add onions and garlic and stir to combine for 1 minute. Add ketchup, water, brown sugar, vinegar, salt and a sprinkle of pepper and stir well to combine. Bring to a boil, then reduce heat to a simmer. Return brisket to skillet, cover and cook over low heat until meat is tender, about 2¸ to 3 hours. Turn the meat over every 20 or 30 minutes to ensure even cooking, redistributing the vegetables (if adding). When meat yields to a fork and is tender throughout, remove from pan and let rest for 10 minutes before slicing. If you prefer a thicker gravy, simmer the sauce while the meat rests, or serve as is. 
-- Adapted from Hadassah cookbook, Rochester, N.Y., chapter

Nutrition:

Per serving: 564 calories (percent of calories from fat, 32), 58 grams protein, 40 grams carbohydrates, 1 gram fiber, 20 grams fat (7 grams saturated), 169 milligrams cholesterol, 1,221 milligrams sodium.