OK, here's an easy but good recipe-
Take the brisket and cover it with water. Cook for 1 hour with lots of chopped up onions (like 4-6 onions) in 400 degree oven.
Then drain and add this marinade: 16 ounces of Apple Cider Vinegar, some brown sugar maybe 1/4 cup, jar of ketchup about a cup plus, jar of something orange like duck sauce or apricot preserves or orange preserves (anything orange). Put this brisket with this marinade back in the oven for another hour probably at 350 - 375 degrees.
Then remove from oven and slice thin. Put back in oven in this sauce all sliced and cook for another hour.
Sometimes it is still not tender enough so if not tender enough then cook more, but it should be fine.
Hope you enjoy it as this is an easy recipe!