This recipe is a winner and one I know I’ll make again. The meat turned out fantastic, with lots of flavor — I especially love the taste and texture of a little whole grain mustard with the tender beef. I made this for a crowd and tripled the recipe to make three whole 6-to-7-pound tenderloins. I divided the meat into 6 roughly even sections and cooked 3 of those per pan in two separate roasting pans. I put one in the oven at one time and then switched. I needed to at least double the cooking time at 450 to around 30 minutes for that quantity of meat, but checked it constantly. The end product was rare to medium rare. Let the meat rest before slicing.
Here’s a picture of the meat seared and seasoned before going into the oven to roast.