Set pressure cooker to saute and add 2 tbsp of olive oil inside. Pat dry your tenderloin and rub minced garlic on the outsides, then sprinkle with salt and pepper and lower into your pot. Brown outsides, then turn pot off and remove pork. Set on a plate.
Pour 1/2 c of your broth into your pot to deglaze = scrape the bottom of your pot with a wooden spatula to get all the little bits loose. (helps avoid the burn notice) Put pork back in with broth.
With the other 1/2 cup of broth add your packet of onion soup mix and whisk together. Pour this on top of your meat. Then sprinkle your sliced onions on top with a sprinkle of salt and pepper.
Close your lid and steam valve and set to manual, pressure, high for 4 minutes. (for 1.5 lb. piece, if much longer I'd increase the time)
Do a natural release for 15 minutes, then a quick release. Take tenderloin out to rest for at least 5-10 min. before slicing to maintain juiciness.
If you want your sauce to be a bit thicker turn Instant Pot to saute again and in a small bowl add some of the hot liquid plus 2 tbsp of cornstarch and whisk together until smooth.
Add back into your Instant Pot and whisk together. Allow to bubble and thicken.
Do that again if you want it a bit thicker with 1 more tbsp. Will thicken a bit more as it sits as well.
Slice pork loin, serve over rice, and spoon french onion sauce over the top of each serving.