Start with a well trimmed tenderloin making sure to remove any of the "silver" skin from the surface. The silver skin is a shiny membrane you typically find on tenderloins. Once you've trimmed the ternderloin you're ready to prepare your jerk rub.
In a small bowl, stir together the thyme, dried onion, allspice, cracked black pepper, cinnamon, cayenne pepper, and salt. Coat tenderloin lightly with oil and rub seasoning onto meat. Set aside to marinate (wrap tightly in plastic wrap and refrigerate for 6-8 hours).
Prepare grill for direct heat grilling over high heat. Once grill is hot place marinated pork onto the hottest part of the grill and cook the tenderloin for about 3 minutes on each of its four sides. Cook just until the pork feels firm and springs back when pressed or an instant-read thermometer reads 145*F when inserted into the thickest part of the tenderloin. Be careful not to overcook it.
Remove from grill and allow to rest for 5 minutes before cutting. Slice in about 3/4" slices and serve.