"This is my go-to recipe for brisket. I usually use bison brisket, but beef brisket works as well. This recipe is easy to prepare and using the pressure cooker greatly reduces cooking time as compared to other methods. The brisket comes out moist, tender, and flavorful, and the gravy is also excellent. I have used this recipe for briskets as large as 6 pounds with equal success, but increased the cook time to 55 minutes. I use an electric pressure cooker for this recipe, but it can also be made in a pressure cooker on the stove. The rub step can be skipped."
Coat beef brisket with beef rub, rubbing it into both sides. Place brisket in a large resealable plastic bag; refrigerate 4 hours to overnight.
Turn on a multi-functional pressure cooker (such as Instant Pot(R)) and select the highest Saute function. Heat oil and lower the brisket into the pot using tongs, fatty side facing down. Cook until bottom is a rich, dark brown, about 6 minutes. Turn and sear until the other side is browned, about 6 minutes more. Transfer brisket to a plate.
Adjust pressure cooker to the medium Saute setting. Add onions, garlic, and salt. Cook, stirring frequently, until onions are soft and beginning to brown, about 10 minutes. Scrape the bottom of the pot as you stir the onions to release the browned bits from the bottom.
Stir broth, wine, ketchup, paprika, thyme, and rosemary into the sauteed onion mixture. Lower the seared brisket back into the pressure cooker, fatty side up. Close and lock the lid; be sure pressure valve is set to the sealed position. Select high pressure according to manufacturer's instructions; set timer for 50 minutes. Allow 10 to 15 minutes for pressure to build.
Release pressure using the natural-release method according to manufacturer's instructions, about 10 minutes. Release any remaining pressure carefully, about 5 minutes. Unlock and remove lid. Transfer brisket to a plate or carving board.
Strain the cooking liquid into a fat separator, collecting the cooked onions and garlic in the strainer. Return the drained onions and garlic to the pressure cooker. Pour the cooking liquid back into the pot, discarding the fat that is left behind. Blend cooking liquid, onions, and garlic into a thick gravy using an immersion blender.
Turn the Saute setting on medium. Mix cold water and cornstarch together in a bowl; pour into the pressure cooker. Cook, stirring frequently, until gravy has thickened, 6 to 8 minutes.
Slice the brisket against in the grain into 1/4-inch slices. Pour gravy over and serve hot.