Have apples peeled, cored, sliced and ready to use.
Season pork tenderloin with steak seasoning. Using the saute setting on the Instant Pot, add 2 tablespoons oil; when the oil is hot and sizzling, add the pork tenderloin, browning it on all sides. Transfer the tenderloin to a plate.
Add remaining tablespoon of oil, the flour and 2 tablespoons of chicken broth to the Instant Pot; cook for 1 minute, stirring as it cooks.
Whisk in the apple juice, remaining broth, cranberries and brown sugar, stirring to bring up any browned particles from the bottom of the pot into the sauce. Add the sliced apples to the pot, then nestle the pork tenderloin on top.
Lock the Instant Pot lid into place and choose the High-Pressure setting for ONE minute, bringing the pot to full pressure. When the timer sounds, immediately unplug the Instant Pot and use a natural release for 10 minutes, followed by an immediate quick release to remove any remaining pressure, if it's still there.
Remove the pork tenderloin to a cutting board and slice into medallions.
Stir the butter into the warm sauce in the Instant Pot. Serve the medallions on a bed of the warm apple cranberry sauce.