Press Sauté function on instant pot. Once hot, add pork butt and brown on all sides for about 10 minutes. Add all of the rest of the ingredients and mix well to combine. Press cancel, secure lid, close off pressure valve then press manual to high pressure and press the up button until the time hits 30 minutes. Once time is up, let the pressure release on its own for 20 minutes, then remove lid.
When the instant pot is slow releasing, turn oven on to broiler.
Use a slotted spoon to remove the fall-apart meat and onions, and place on a baking sheet. Use two fork to pull apart the meat slightly. Squeeze fresh lime juice on top and place under the broiler to cook for just a few minutes or until the pork begins to brown and crisp.
Garnish with fresh lime wedges and cilantro before serving!