1. Saute the peppers and onions, deglaze with beer: Heat 1 tablespoon of oil over saute mode until it is shimmering. (Medium heat in a stovetop PC.) Add the onions, peppers, and garlic to the pot and stir to coat with oil, then sprinkle with 1/2 teaspoon of salt. Saute until the onions soften, about 5 minutes. Pour the beer into the pot and scrape the bottom of the pot with a wooden spoon to loosen any stuck bits of onion. Bring the beer to a boil for 1 minute to boil off some of the alcohol.
2. Slice and season the flank steak, then add to the pot: While the peppers and onions are cooking, slice the flank steak into 2 inch pieces and sprinkle with the salt and Ancho chile powder.
3. Pressure cook on high for 30 minutes with a natural pressure release: Stir the beef into the pot. Lock the lid and pressure cook on high pressure for 30 minutes in an electric PC or 24 minutes in a stovetop PC. Let the pressure come down naturally, about 15 more minutes.
4. Shred the beef and serve: Scoop the beef and vegetables to a platter with a slotted spoon. Pour the pan juices into a gravy strainer and let settle. Shred the beef with forks, then pour just enough of the defatted pan juices over it to make it wet. Serve with taco fixings and enjoy!