In an oven-proof pan heat oil and butter over moderately high heat. Sear pork in pan turning to brown all sides, about 6 minutes total. Pour off fat. Set aside.
Combine all sauce ingredients in a large measuring cup and puree with a hand blender. Pour sauce over pork in the pan. Bring to a boil over medium high heat on the stove.
Cover pan with foil and transfer to oven. Cook 25-30 minutes until internal temperature measured with an instant-read thermometer is 145°F.
Remove from oven and let meat rest, covered, for 10 minutes.
Cut tenderloin into thick slices and serve with sauce.