Preheat oven to 325

Line a 9x13 pan with foil

Set brisket in pan and sprinkle top and bottom with salt and pepper, rub in

In a medium bowl add vinegar, water, tomato sauce, brown sugar, garlic, and onions - mix until fully incorporated

Lift brisket up and pour half the sauce in the bottom of the pan

Place brisket back down and pour other half of the sauce over the top of brisket

Cover entire pan with two layers of foil, sealing tight

Place in oven and bake at 325 for 3 to 3 1/2 hours (meat should be tender, at minimum temperature of 170 degrees, and easily cut)

Remove from oven, drain sauce into a medium pot

Let brisket set for 30 minutes before cutting - cut against the grain to serve

Bring sauce to a boil and let simmer for 20 minutes or so to reduce

Serve brisket with sauce