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1
Season the prime rib liberally on all sides with salt and black pepper.
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2
Line a roasting pan with heavy-duty aluminum foil and position a roasting rack inside of it.
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3
Transfer the prime rib fat side up to the middle of the roasting rack. Tent the prime rib loosely with foil, and allow it to stand at room temperature for 1-2 hours.
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4
Pro tip: Allowing the prime rib to sit at room temperature will help it cook more evenly.
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5
Preheat the oven to 500u00b0F.
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6
Place the Dijon mustard, horseradish, garlic powder, thyme, rosemary, and onion powder into a small bowl. Stir to combine.
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7
Using the back of a spoon, spread the mustard mixture over the top surface of the meat.
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8
Roast the prime rib for 20 minutes on the middle rack of oven.
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9
Reduce the oven temperature to 325u00b0F. Continue roasting the prime rib for 75-100 minutes longer, or until the meat reaches an internal temperature of 120-145u00b0F, depending on desired doneness. (Pro tip: Remove at 120u00b0F for a more medium-rare prime rib, and remove closer to 140u00b0F for a more well done prime rib. Note that the temperature of the meat will continue to rise by about 5u00b0F after removal from oven.)
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10
Check to see that prime rib is done. Remove from oven or add time as needed.
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11
Allow the prime rib to rest on the rack for 15-30 minutes.
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12
Transfer the prime rib to a cutting board and untie. Carve and serve immediately. Refrigerate leftovers up to 5 days or freeze up to 6 months.
