In a small bowl, combine the thyme, garlic powder, rosemary, salt, and pepper.
Trim the pork tenderloin of the silver skin, if needed, by running a sharp knife under the membrane and pulling it off the tenderloin. (You can ask your grocery store butcher to do this for you if preferred.)
Pat the pork dry with a paper towel, then rub 1 teaspoon of oil all over it. Sprinkle seasoning mixture all over pork to cover.
Select the ‘Saute’ feature on the Instant Pot. Add the remaining 2 teaspoons of oil to pot and let it heat for 1 minute. Add the seasoned pork and brown on all sides, about 2 minutes per side. Remove the pork to a plate.
Pour the stock into the pot and deglaze by scraping any brown bits off the bottom of the pot with a spoon. Press ‘Cancel’ to turn the pot off. Return the pork to the pot.
Secure the lid, making sure the steam valve is sealed. Cook under high pressure for 2 minutes. Let the steam naturally release for 12 minutes. (If the pot finishes releasing early, keep the lid on until for the full 12 minutes.) Manually or quick release any remaining steam. Check the pork for an internal temperature of 140°F. (See Notes if the temperature is lower.)
Remove the pork, reserving the liquid in the pot, and let it rest on a cutting board while making gravy. (The pork will continue to cook while resting to reach an internal temperature of 145°F.)
For the Gravy:
Whisk together the cornstarch and water in a small bowl. Select the ‘Saute’ function and bring the cooking liquid to a simmer. Whisk in the cornstarch slurry and simmer while whisking until translucent and thickened, 1 to 2 minutes. Turn off the pot.
Slice the pork and serve with the gravy.
Notes
Vary the seasonings. For a sweet and smoky flavor, add 1 teaspoon each of brown sugar and smoked paprika to the seasoning mixture. You can also use finely chopped fresh herbs instead of dried or swap the dried herbs I used for Italian seasoning.
Scrape browned bits. When deglazing, be sure to scrape browned bits from the bottom of the pot to avoid the Burn warning.
The pressurized cooking time may seem short, but it will do most of the cooking during the pressurizing and the natural release times. This will yield a very juicy tenderloin with slight pink still in the meat. As long as the pork has reached 140°F internally, the pink center is okay!
If the internal temperature is less than 140°F at the end of Step 6, after checking with a meat thermometer, cook again under High pressure for 1 minute and manually release the steam after cooking.
Let the Instant Pot pork tenderloin rest. The pork will continue to cook while resting to reach the correct internal temperature of 145°F. Letting the pork rest also allows the juices to reabsorb and redistribute, so each bite is incredibly juicy. If you cut into the meat too quickly, all the juices will run out.
Change up the flavor of the gravy. Swap some of the chicken broth for white wine for a bright twist. You can also add 2 tablespoons of apple cider vinegar to the stock for a hint of acidity. Or, 1 teaspoon of soy sauce in the gravy adds a subtle umami flavor.