Remove the Silverskin from Tenderloins. Whisk together Marinade ingredients and rub into tenderloin(s). Set aside.
Whisk together Balsamic Vinegar Reduction ingredients and set aside.
Use the Sauté or Browning function on your Instant Pot or Pressure Cooker and wait about 3 minutes to allow the pot to fully heat.
Add oil to cooking pot.
Lightly dredge tenderloins through potato starch.**
Quickly sear tenderloins, one at a time, on all sides and ends until slightly browned, about 1-2 minutes each. Remove Tenderloins to a plate.
Pour in apple cider and scrape the bottom of the pot to deglaze the pot, making sure to loosen all the brown bits.
Pour in 1/4 cup of the the balsamic vinegar mixture and cinnamon stick. Simmer for one minute and then turn off Pressure Cooker.
Return tenderloin and any juices, to the cooking pot and place apple slices on top.
Lock on lid and close pressure valve. Cook at Low Pressure (most machines default to high) for 0 minutes.
When Beep sounds, wait 5 minutes and then release the rest of the pressure.
Remove tenderloins and apples to a plate. Tightly cover tenderloins with foil to allow juices to redistribute.
Select Sauté/Browning and whisk in the rest of the balsamic vinegar mixture. Simmer until sauce has reduced by about 50%, or until think and syrupy.
Add butter and whisk in well.
Slice tenderloin and spoon sauce over top. Place apples on the side.
**The potato starch is optional. It can be used for dredging or for after pressure release (as a slurry), or not at all.If the pork is over cooked, it means that your seared the tenderloin too long before closing the lid to pressure cook. Next time, just sear for less time. :)If pork is too pink for your liking, place slices into the hot sauce in the pressure cooker, which will slowly cook it more.
Side Dishes to Serve with Balsamic Apple Pork Tenderloin: