Recipe courtesy of Nancy Josland DalsinPreheat oven to 450 degrees F.
Pat the room-temperature prime rib roast dry with paper towels or napkins. Smear the cut ends only of the roast with the butter.
Place the roast, ribs down or fat side up, in a heavy stainless-steel Roasting Pan or other metal roasting pan, ( I always use a cast iron skillet.)
Sear the rib roast for 15 minutes at the higher oven temperature (450 degrees F.), then turn the oven to the lower temperature (325 degrees F.) for the rest of the cooking time. Every 1/2 hour, baste the cut ends of the roast with the fat accumulated in the roasting pan. Do no cover the roast.
About 45 minutes before the estimated end of the roasting time, begin checking the internal temperature (use a good instant-read digital meat thermometer).
Beef Roast Cooking Temperatures:
Rare
120 to 125 degrees F
center is bright red, pinkish toward the exterior portion
Medium Rare
130 to 135 degrees F
center is very pink, slightly brown toward the exterior portion
Medium
140 to 145 degrees F
center is light pink, outer portion is brown
Medium Well
150 to 155 degrees F
not pink
Well Done
160 degrees F and above
steak is uniformly brown throughout
Remember, the rib roast will continue to cook as it sets. The temperature will rise to 125 degrees F. to 130 degrees F. internal temperature (medium rare) at 15 to 20 minutes.