Pat the pork tenderloins dry with paper towels and trim off any visible silver skin so the meat stays tender after grilling.
In a small bowl, whisk together the olive oil, apple cider vinegar, brown sugar, salt, pepper, onion powder, garlic powder, smoked paprika, and Italian seasoning until they are all well combined.
Place the tenderloins in a zip-top bag or shallow dish and pour the marinade over them. Massage them gently so as to coat all sides evenly. Refrigerate the pork for 2 to 6 hours. Remove the pork from the refrigerator about 30 minutes before grilling.
Preheat the grill to about 400 degrees F and set it up for two-zone cooking so you have both direct and indirect heat.
Remove the pork from the marinade and discard the used marinade, then place the pork over direct heat and sear them for about 1½ to 2 minutes per side until they are lightly browned.
Transfer the pork to the other side of the grill, cover, and cook them for 12 to 16 minutes, until the internal temperature of the pork reaches 140 to 142 degrees F. Start checking the temperature at the 10-minute mark.
Transfer the pork to a cutting board and tent them loosely with foil. Let them rest for 10 minutes so the juices redistribute and the temperature rises to about 145 degrees F.
Slice the pork against the grain into about ½-inch medallions and serve.