Place tenderloin on cutting board and, using a sharp knife, remove the “silver skin” membrane that runs lengthwise on one side of the tenderloin so it doesn’t tighten and twist the roast. With knife blade under membrane, slowly shear it off and pull it away, avoiding cutting into meat as much as possible.
Cover butterflied tenderloin with parchment, and use meat mallet to thin it out a bit and make it even in thickness. Sprinkle with salt and pepper.
Place stuffed loin in pan and cook 15 minutes to brown top, then reduce oven temperature to 325 degrees F and cook uncovered 30 to 40 minutes, until roast reaches an internal temperature of 140 degrees F.