Take the tenderloin out of the refrigerator, pat it dry and rub it gently all over with salt and pepper.
Let rest for 30 minutes before cooking.
Heat your oven to 425.
Put the tenderloin on a rimmed baking sheet and put it into the oven.
It will take less than an hour to roast the meat to Medium Rare; start checking temperature in the center of the meat at the 30 minute mark.
Roast until your thermometer reads 130 for Medium Rare; the meat will continue cooking as it rests, reaching 135 degrees for a perfect medium rare.
Take the tenderloin off of the pan and let it rest on the cutting board or another pan for 30 minutes under loosely tented foil before slicing to serve.