Preheat the oven to 425 degrees and set your gas grill (if you have one) to high
Get your whole beef tenderloin ready - I usually buy an untrimmed, whole tenderloin - it's less expensive I find the whole tenderloin is easy to trim and it roasts beautifully. (for my Twin Cities readers, Morelli's in St. Paul has the best price in town) If you prefer, ask your butcher for a whole, trimmed beef tenderloin.
Dry any juices off the tenderloin before trimming. Find your sharpest knife - it will make the trimming fast and easy
Trim the silver skin from the tenderloin. It's easy to see and it's tough, so you want to remove it before you cook the meat
Trim any large pieces of fat from the tenderloin
Use kitchen string to incorporate thin end pieces on the end (like a tail). Just fold it underneath the tenderloin and tie it up.
Continue to tie the roast in a few places. This will help to ensure the roast cooks as evenly as possible. And… it looks cool!
Brush the tenderloin with the 1 tablespoon of olive oil on both sides
Sprinkle the meat on both sides with the 1 teaspoon of kosher salt and 1/2 teaspoon of ground black pepper.
Now for the searing. I like to sear the tenderloin on my gas grill - it's fast, easy and convenient. If you don't want to use the grill, sear it in the roasting pan on the stove. Either way, sear it just long enough to get some color on the meat - about 4 minutes per side. Searing the meat will help to seal in the juices as it roasts
Roast the tenderloin on a rack (if you have one) in a roasting pan, or on a sheet pan. It will take between 30 and 50 minutes, depending on your oven and how well-done you want the meat
Dig out your meat thermometer. This is a critical instrument when cooking large pieces of meat - you can find one at any hardware store, cooking store or Target.
Roast the meat for 20 minutes and check the temperature. You'll want to cook it to 130 in the thickest section for medium-rare. (125 for rare, 135 for medium) After that first look, I check the temperature every 10 minutes to be sure I don't over cook it. Because tenderloins are not completely even, the end pieces will be more well done than the thickest section
Once the tenderloin is roasted, let it rest for 20 minutes or so to let the juices absorb into the meat
Remove the strings (I've forgotten that a couple of times - not too tasty!)
Carve the tenderloin into to thick slices
Serve the beef with the Mustard Horseradish Sauce (see below) and add your favorite potatoes, vegetables and salad