Preheat oven to 425° and line the bottom of the roasting pan with aluminum foil.
To crack whole peppercorns, you can use a coarse setting on the pepper mill, pulse it a few times in a spice grinder, or use a heavy cast iron skillet to crack it by hand on the cutting board.
Prepare Beef Tenderloin:
Use cooking twine to tie the tenderloin all along the whole length in 1-inch intervals. Make sure not to tie too tight where it starts cutting into meat.
Rub tenderloin with a little bit of olive oil all over.
Spread all the seasoning on the parchment paper, add grated Parmesan cheese, mix it evenly, and place the tenderloin on top of the seasoning. Roll the tenderloin around to coat it evenly in seasoning and press on the seasoning to stick it on better.
Cooking Beef Tenderloin:
Once beef tenderloin is tied and coated with seasoning, place it onto the rack inside the roasting pan.
Insert a leave-in thermometer though the side towards the center of the meat. (If you don’t have a leave-in thermometer, you will need to take the meat out of the oven to take the temperature. Close the oven so the oven temperature doesn’t lower. Remember to take the temperature of the center, at the thickest part.)
Cook beef tenderloin until it reaches 130°-135° for medium-rare or 140°-145° for medium.
Take the tenderloin out of the oven and transfer onto the cutting board. Cut off the twine and gently take it off, trying not to take off the seasoning. Loosely tent with a sheet of aluminum foil and let it rest for 10-15 minutes before cutting.
Slice tenderloin into about 1/2 inch slices, against the grain.
When buying the roast, ask the butcher to cut you a 2 pound beef tenderloin roast, center cut (or a 2-pound chateaubriand roast). Specify that you need a center cut, not the tail end. You can also ask them to tie it for you if you don't feel conformable doing it yourself.
Medium-rare or medium is the best temperature for beef tenderloin. You don’t want to cook this beautiful and expensive cut of meat to more than medium. For medium-rare, cook it to 130°F-135°F. For medium, cook to 135°F-140°F. And for rare, cook it to 120°F-125°F.
Remember to REST the steak for 5-10 minutes after cooking and slice your steaks against the grain.
Storing: Make sure to store your leftover beef tenderloin slices in an airtight container, in the refrigerator. Properly stored, leftover beef tenderloin should be good for up to 4 days.
Reheating: Preheat your oven to 350°F and wrap each individual slice of beef tenderloin in foil. Try not to wrap it too tight! Place the wrapped tenderloin pieces directly onto the oven rack and reheat for 10-15 minutes. The exact time depends on the thickness of cuts. Reheat it just until warm in the middle so it doesn’t overcook.