This beef rib roast, although commonly called Prime Rib, is not usually of Prime quality unless you’re eating in a restaurant. But Choice Rib doesn’t sound as good, and why quibble with tradition? Anyway, it’s formal name is Standing Rib Roast.
Yes, you can roast a prime rib at home that tastes very nearly as good as you get at an expensive restaurant. The key is the roasting temperature and time.
If the oven is too cool, the roast will cook to a nice even pink color inside, but the outside won’t have the yummy brown crust that you probably want. But if you cook it at a high enough temperature to brown the outside, it will cook unevenly inside, from brown (well-done) at the edges to red (rare) in the center.
What to do? The same thing you do for a thick steak. Brown it first in the frying pan, and then put it in a medium oven.
Sprinkle the outside of the roast with garlic salt and pepper, heat up the skillet with some vegetable oil in it, and pre-heat the oven to 250 F. Using tongs, brown the roast a few minutes on each end and on the fat side. Set the roast aside to cool off a little, and use the skillet to brown some onion chunks and some beef bones or oxtails, if you’re going to serve the roast Au Jus. Add some tomato paste, garlic salt, and pepper to the pan, and stir while the stuff browns. When they are browned, add the onions and bones to the roasting pan around and under the roast.
Place the roast fat side up in a roasting pan in the oven. If it’s a boneless roast, like they sell now at CostCo, put the roast on a rack.
Check its doneness with a meat thermometer, and stop when it gets to 120 degrees for rare or 130 degrees for medium rare. The internal temperature will continue to rise while the roast sits on the cutting board for at least 30 minutes. You should always let roasts and turkeys rest for 15-30 minutes before carving to let the meat re-absorb some of the juices released during cooking.
During the sitting time, you can make the Au Jus sauce and, if you want, Yorkshire Pudding to go with the roast. (Yorkshire Pudding is the same as popovers, except popovers are made with butter and Yorkshire Pudding is made with the beef fat. Man, is it good sopping up the jus with the pudding!)
The time in the oven should be roughly 2 to 2 1/2 hours for a medium rare seven to eight pound roast. Allow another half hour to finish the Au Jus and Yorkshire Pudding.