Perfect Celebration Entree

This is my favorite splurge-worthy main course to make for a crowd. It's easy, delicious, and can feed a large group with ease (while having many beautiful next-day uses if there are leftovers). I use a charcoal grill, but a gas grill will work too. Start by preheating your grill to 450 degrees.

1 beef tenderloin, trimmed
1/2 cup grainy Dijon mustard (I really like Téméraire)
2 tablespoons kosher salt
1 tablespoon coarsely ground black pepper
3 tablespoons (small handful) of chopped fresh rosemary
3 cloves garlic, finely chopped (jarred garlic is just fine)

Start by patting the tenderloin dry with a clean kitchen towel. If the tenderloin is much thicker on one end than the other, there are 2 options. You can either truss the thinner part of the tenderloin by folding it under and tying it with butcher's twine (see photo). Otherwise, feel free to cut the tenderloin into two pieces (one thicker and one thinner) so you have more control over the cooking process. I actually appreciate having a tenderloin that varies (slightly) in thickness, as this allows people to choose a slice that is more or less done according to their preference.

In a small bowl, combine mustard, garlic, salt and pepper.  Evenly coat the tenderloin with this mixture. Then evenly apply the chopped rosemary, patting it in so it sticks. Make sure your grill is clean. Feel free to spray it with non-stick cooking spray (they make it specifically for the grill's high temperatures now). Place the tenderloin on the grill. Rotate every 5-7 minutes, forming a nice brown crust on all sides. Once it is seared on all sides, move it to a  more indirect place on the grill to continue cooking. It will need to cook about 15 minutes per pound (including the searing time), and follow these guidelines with your meat thermometer (put it into the thickest part, realizing the rest will be slightly more done):
Good grainy Dijon is key

Rare - 120 degrees F 
Medium Rare - 125 degrees F
Medium - 130 degrees F (this is overdone for tenderloin in my opinion! Go with R or MR)
 
The most important step is now. Let the meat rest at least 15 minutes (don't cheat). This will make sure the tenderloin is moist by letting the juices redistribute after cooking. Slice the meat against the grain. I make the slices thinner as my crowd gets bigger (it makes it go further). I serve it with a couple sides from the following list:

-grilled vegetables (any that I have in my fridge: broccolini, peppers, onions, mushrooms, zucchini, eggplant, etc)
-broccoli slaw (you can buy the slaw mix in the produce aisle and just add a nice dijon or ginger-soy vinaigrette)
-grilled red potatoes (I steam them first to speed up the time they need on the grill)

Sometimes I make an herbed butter to drizzle over the meat when it's finished. I also make sure there is a lot of crusty sourdough bread with horseradish, mustard, and various dipping oils. Celebration meal, done!