Preheat oven to 425 degrees F.
Season tenderloin on all sides with 1 1/2 teaspoons Chinese five-spice powder, salt, and pepper. Place tenderloin in shallow pan and roast for about 20 minutes, or until internal temperature reaches 155 degrees F. Remove pork from oven and let rest 5 minutes.
While pork is cooking, core and thinly slice apple. Thinly slice onion.
While pork is resting, in a large bowl, whisk together vinegar, oil, and remaining 1/2 teaspoon Chinese five-spice powder. Add salad greens, apple, and onion and toss. Season with salt and pepper to taste if desired. Arrange salad on plates or a platter
Cut pork into thin slices. Arrange on top of salads and serve.
