In a large Ziploc Bag, add olive oil, apple cider vinegar, garlic powder, onion powder, salt, pepper, Italian seasoning and mix until combined.
Add the pork loin.
Seal the bag and shake it around until meat is coated.
Marinate for 20-30 minutes at room temperature.
Add oil in an Instant pot.
Turn on the "Saute" mode.
Remove pork from the Ziploc bag and transfer to the pressure cooker. Discard the remaining marinade.
Sprinkle salt, pepper, Italian seasoning and garlic over the meat.
Cook each side of the meat until browned but it should not be cooked through. Be careful not to burn the garlic. It can be added near the end of the browning phase.
Remove from pressure cooker and transfer to a plate.
Add broth to deglaze the pot and use a wooden spoon to scrape up any brown bits.
Place a trivet in the pot.
Place the browned tenderloin on top of trivet.
Top with slices of butter.
Put the lid on and turn the valve to “Sealing.”
Select “Manual” mode and set the timer for 1 minute.
When the cook time is over, allow pressure to release completely naturally. This takes about 15 minutes. Do not do a quick pressure release. This slow release allows the pork to continue cooking.
Test the pork for doneness with a meat thermometer. Pork is considered cooked at 145 degrees F. If it's undercooked, put the lid back on but don't turn on the pressure cooker. The residual heat will cook it through to the correct temperature in about 3-5 minutes.
Remove pork loin from the instant pot to a cutting board.
Cover and let it rest for 10 minutes.
Then, slice and enjoy.
Optional: Make gravy with the remaining broth and pork drippings. Simply mix in a cornstarch slurry (1-2 tablespoon cornstarch dissolved in 1-2 tablespoon water) in the liquid left behind in the pressure cooker. Cook uncovered on the "Saute" mode while constantly mixing until gravy is thickened to your desired consistency. Serve this alongside or on top of your cooked loin.