OK, here is my completely unofficial theory on how Brisket became associated with Passover (and Rosh Hashana and Hanukah) among Ashkenazi (Eastern European) Jews. (Sephardic Jews have completely different dietary traditions.):
Getting their hands on an entire piece of meat was such a rare and wondrous thing, it was reserved for major holidays. That's it. Seriously, no religious significance whatsoever AFAIK (other than laws of kashrut saying that you should only eat the foreshank of an animal, never the back end). Sephardic Jews eat lamb on Passover, maybe for the same reason, IDK, because I'm really not all that familiar with their traditions. On Rosh Hashana, brisket is often combined with prunes, apricots, carrots or winter squash to make Tzimmes, for a sweet new year. It's heavenly, but my husband's totally assimilated family hates it so I never make it anymore.
That said, here's my favorite holiday brisket recipe. I have another that is much more involved and also just as delicious, but I rarely have the time to deal with it!
Brisket Amy's Way3 onions, sliced thinly
4- 5 lbs. first cut beef brisket
2 cloves of garlic, sliced thin
1 cup red wine (I use something dry, that I would like to drink)
2 cups OJ
Box of Pomi tomato sauce (or whatever you like to use)
Lawry's season salt
Garlic Powder
Paprika
1 tsp. sugar
If possible, the night before you are going to cook the brisket, place it
fat side up and place small slits in the meat. Place thin slices of garlic in the slits. Season to taste with the season salt and garlic powder.
The next day, heat a dutch oven over medium heat, and place the brisket in the pan
fat side down, to sear it. When lightly browned, turn over and repeat on other side.
Preheat oven to 325.
Remove from pan. Place sliced onions in the pan, and place the brisket
fat side up on top of the onions.
Mix the wine, OJ, tomato sauce, sugar, and a generous dash of paprika. Pour over the brisket, and bring to a gentle simmer.
Cover tightly, and place in the warmed oven for 2 1/2 - 3 hours. Raise heat to 350, remove cover, and cook for another 1/2 hour - 45 minutes.
Remove meat, and refrigerate until next day, when you will allow it to come up to room temp and then slice thinly across the grain. Allow the gravy to separate in the fridge, and the following day skim off the fat. Then place the sliced meat in a large baking dish, pour the skimmed gravy over and re-heat (covered very loosely and vented) until hot and the meat starts browning again.
The original recipe calls for 1/2 the liquid, but my family loves gravy, and with this amount I never have to add water because the pan is burning. If it seems like too much liquid and it is boiling instead of braising, just cook uncovered for longer; the liquid will evaporate. Enjoy!