Preheat oven to 350. In a small bowl, mix together salt, pepper,cumin, chili powder and cinnamon. rub this into the tenderloin and let it sit for atleast an hour. I have let mine sit overnight and was really good that way too.
Heat olive oil in ovenproof heavy skillet. I used my cast iron skillet.Put pork in and brown all sides, about 4 minutes total. Remove from heat, leaving pork in the pan.
Make the glaze then press over the top of tenderloin (the glaze will look dry, but its ok, it wont be) I know this doesnt look like a glaze, more like damp brown sugar, it will turn to a glaze when it melts. Place skillet in the over and roast for about 20 minutes til center reaches 140 degrees. let pork sit in pan on top of stove, covered in foil, for about 10 minutes. Slice and serve.