Set your pressure cooker to sauté function. Once the pot is hot, you can add olive oil and sliced onions. Sauté the onion in the oil until translucent (about two and a half minutes).
While the onions are sautéing, you can rub your pork rub (or seasoning) over the pork.
Use a wooden spoon to move the sauteed onions to the sides of the pot and then place your seasoned loin into the pot. Sear the pork loin until browned on all sides (about two and a half minutes per side). You may need to add more oil as needed.
Remove the browned pork and onions from the pot.
To deglaze, add your water to the pot and then use your wooden spoon to scrape the bottom of the pot to remove any cooked-on pieces. You can then return the pork loin and onions to the pot.
Pour half of the barbecue sauce (one cup) over the pork loin and then place the lid on to your pot. Lock the lid and in place and then set the valve to sealing. Cook your loin on high pressure for 35 minutes.
Once the cooking time is up, you can allow for a natural pressure release for about 10 minutes, then carefully quick release any remaining pressure.
Carefully use two forks to shred or pull apart the cooked pork .
Serve your shredded pork loin on a bun, roll, or as desired with the remaining sauce.