Remove silver skin from pork tenderloin and then place pork in a gallon-size zip top bag. Add in the salsa, vinegar, and Worcestershire sauce. Remove air from bag, seal, and smush everything around to coat the pork and mix up the marinade. Refrigerate for 3 hours.
Heat grill to 400+ degrees F. Remove pork from bag, shaking off excess marinade, and place on grill. Cook pork for 25-30 minutes, turning once, or until internal temperature reaches 150 degrees F.
Remove pork from grill to a plate or baking sheet and loosely tent with foil.
While the pork rests make the salsa. Remove pit from peach and seed from avocado. Dice both peach & avocado and place in a small mixing bowl. Add onion, lemon zest, and parsley. Stir to combine. Season with salt and pepper to taste.
Cut the pork tenderloin into 1/2-inch slices. Plate pork and top with salsa for serving.
You can marinade your pork roast up to 8 hours, but you want to get at least an hour of marinade time before grilling.I used raw onion for this recipe. Rinsing them under cold water removes a lot of that onion sting. If you prefer, you can cut the whole (peeled) red onion into thick slices and grill them while the pork cooks until the onion is soft. Then chop the grilled onion and add it to the salsa.