Rub tenderloins with salt and pepper. Place on a baking sheet and drizzle lightly with olive oil. Roast pork for about 20 minutes, turning once. Remove from oven, place on a plate, tent with foil and let rest for 5 minutes.
Slice pork into 1/4" thick slices and arrange on plates with an apple-onion mixture. Sprinkle with parsley and serve.