I used Alton Brown’s Tender is the Loin episode to learn how to trim a whole tenderloin. But I use his recipefrom the Salt episode to create a wonderfully seasoned roast every Christmas. My family loves it. It is practically melt in your mouth good. I cook it to medium rare. I do the same with the head roast and cook that to medium/medium well for my dad who gets grossed out with the pink meat.
Just remember, you don’t eat that crust. It is nasty! Also, be sure to sear all sides of the tenderloin before roasting. I forgot to do that the first time and it tasted so much better the next time when I remembered to do that.
For any left overs, do not reheat the next day. It tastes slightly different, but equally amazing cold.
I fry up all the fat and gristle that I trim off for the dogs. That becomes their Christmas treat.