In a large zip baggie, mix soy sauce, sugar, sherry, onion powder, cinnamon, olive oil and garlic powder. Swish around to mix. Add the pork and seal the bag. Refrigerate to marinate at least 6 hours, or overnight.
Preheat the oven to 400℉. Spray a medium casserole dish with nonstick spray.
Drain the pork, reserving the marinade, and place it into the dish. Pour a little of the marinade into the dish with the pork. Bake the tenderloin 25 to 35 minutes, or until meat thermometer registers 145° F. Slice into medallions.
Heat marinade to boiling and drizzle it onto the pork (if you wish).
Notes
The tenderloin may also be grilled. Place tenderloins on oiled grill and cook 20 minutes, or to desired doneness.
If you are preparing this recipe as GLUTEN-FREE, just be sure to use GF soy sauce.