Turn the cooker to the high saute setting and add the avocado oil to the pot.
Cut the roast into 2 or 3 large pieces. Sprinkle the sea salt over the meat. Put the roast pieces into the pot and sear on two sides, 3-4 minutes each. Turn the cooker off.
Add the onion to the pot. Whisk together the vinegar, garlic, and tomato paste and then pour it over the beef. Sprinkle the black pepper and red pepper flakes on the meat and lay the rosemary on top.
Close the lid and the steam valve. Set the cooker to high pressure for 60 minutes. Let all the pressure release naturally 0 this should take 15 to 20 minutes.
Transfer the beef to a large plate and break it up into large 2 to 3-inch pieces.
Turn the cooker to high saute. Whisk together the beef broth and tapioca flour and while whisking the pot juices, slowly add the broth slurry. Cook for 2 to 3 minutes until the juices become bubbly and slightly thickened into a gravy.
Serve the beef with the gravy (mashed potatoes are highly recommended here).