Cut pork tenderloin into 8 pieces, like "steaks," about 4 inches wide. Season both sides of medallions with salt, pepper and thyme.
Heat a tablespoon of olive oil in a large frying pan over medium heat.
Add pork to pan and cook until browned on all sides, turning as necessary about 6-8 minutes.
Transfer pork to an oven-safe baking dish and bake until at least an internal temperature of 145ºF about 10-12 minutes.
Meanwhile, core apple and chop into ½-inch pieces.
Using the same skillet you cooked the pork in, melt 2 tablespoons of butter over medium heat. Add apples and cook until golden, about 5-7 minutes. Season with salt and pepper.
Stir in stock and increase heat to medium-high and continue cooking until stock thickens and apples are tender, another 3-4 minutes.
Once pork finishes cooking, transfer to a platter and top pork slices with apple mixture.
Notes
Any type of apple can be used. Honeycrisp, Gala, and Fuji apples are my favorite.
Pork should be cooked to an internal temperature of at least 145ºF before resting. Time will vary based on thickness.