Mix the balsamic vinegar with the next 6 ingredients in a small bowl.
Place pork tenderloin in large ziploc bag. Carefully pour in marinade. Allow it to marinate for at least 30 minutes or longer if you have time. (overnight is best)
Preheat oven to 400 degrees.
Heat 2 tablespoons vegetable oil in cast iron skillet over medium high heat. Carefully place pork in skillet and brown on all sides (2 minutes per side, about 8 minutes). Add in pear slices around pork.
Bake in oven for 15 minutes or until juices run clear and it is cooked through.
Let rest for 5 minutes before slicing.
Notes
*If you can find a flavored balsamic vinegar with cinnamon it's even better!