Preheat oven to 425 degrees F. Sprinkle tenderloins with salt and pepper. In a deep oven-proof skillet, heat the oil and sauté the onion until translucent.
Add tenderloins and brown on all sides. Stir together remaining ingredients in a small mixing bowl and add to skillet. Cover with oven-proof lid or foil and place in oven.
Cook pork for 20 minutes or until the internal temperature as measured with a meat thermometer is 150 degrees F. Remove from the oven, allow to rest 10 minutes before carving. Spoon sauce over tenderloin slices.