Grill: Preheat the grill to a high heat (around 550 degrees F).

Prep: Tie beef tenderloin with kitchen twine (see video tutorial here or photo tutorial above within body of post). Let beef come to room temperature (approx. 30 minutes - 1 hour).

Mushroom Sauce: Bring a large cast iron skillet to a medium-high heat, add 4 tablespoons butter and let melt. Add mushrooms to the hot pan, season with salt, and move around until fully cooked. Add another 4 tablespoons of butter along with garlic and shallots. Let soften. Add broth, cream, and wine along with peppercorns, fresh thyme, and lemon zest. Bring to a gentle simmer, stirring frequently, until it has thickened a bit, approx. 15-25 minutes or until sauce coats the back of a spoon. Remove from heat and add sour cream; stir to combine. Taste and add kosher salt and ground black pepper, as desired. Cover and keep warm until serving. 

Dry Rub: Put all of the dry rub ingredients in a small bowl and mix together. Coat the outside of the tied beef tenderloin with the dry rub.

Grill: Place the seasoned tenderloin on the hot grill to sear for 2 minutes on each side. Reduce the heat to about 400 degrees F, move tenderloin to indirect heat and let it cook for an additional 10-15 minutes or until the internal temperature at the thickest part of the meat reaches 125 degrees F. for a medium-rare finish (use a meat thermometer).

Rest: Transfer the beef tenderloin to a baking sheet or cutting board to let the meat rest 10-15 minutes. 

Serve: Use a scissors to remove the kitchen twine and cut into thick slices. Enjoy with the Creamy Mushroom Sauce on top of each slice.