Add 2 tbsp red wine vinegar to the pot, using a wooden spoon to scrape up the brown bits.
Pour in 2 cups of beef bone broth. Return the roast to the pot and add the diced onion, potatoes, and carrots (if using).
Close the lid and set the pressure valve to seal. Cook on high pressure for 20 minutes per pound of roast (40 minutes total). Allow a natural release for 12 minutes.
Remove the roast and vegetables. Turn the Instant Pot to soup mode. Mix 2 tbsp cornstarch with 1/2 cup cold water to create a slurry. Whisk into the boiling liquid until thickened.
Slice the roast and serve with potatoes and carrots. Drizzle with the thickened gravy.