Prepare the Prime Rib:

Pat the prime rib dry with paper towels.

Rub Dijon mustard all over the surface of the meat.

Season with Salt & Seeds:

Mix kosher salt with mustard seeds.

Press this mixture evenly over the mustard-coated rib.

Add Onions & Rosemary:

Arrange onion slices around the roast.

Tuck a few rosemary sprigs (optional) under the rib and onions for added flavor.

Roast the Prime Rib:

Preheat oven to 450°F (230°C).

Place the rib in a roasting pan, fat side up.

Roast for 15 minutes at high heat to sear, then reduce oven to 325°F (160°C).

Continue roasting about 13–15 minutes per pound for medium-rare, or until a meat thermometer reads 130°F–135°F (54°C–57°C).

Rest the Meat: