Updated: Aug 7, 2020
Place you roast on a tray that has edges (not like the one shown) that can catch any of the juices that may come out and leave it for 4 to 6 hours so it can come to room temp.
Ok, first of all the Meat does NOT have to be Prime cut of beef to be called Prime Rib, this is a Choice cut so its a Rib Roast NOT Prime Rib roast, the name Prime dates back prior to the USDA rating scales…there are three grades of beef, Prime, Choice and select…most stores only have Choice and select, butcher and specialty meat stores will have Prime meat for a much higher dollar…
while waiting for it to get to temp if your meat department hasn’t done it for you, separate the meat from the bone starting from the thinner part where the ribs are sticking out cutting back to almost the end and butterfly it leaving the back end still connected, season the meat and ribs well with what ever you like, I use 1 cup coarse sea salt (no salt with the interior mix as it will draw out much desired moisture), 1/2 cup pepper, 2 tbsp garlic, powder (prefer 6 to 8 cloves diced and smashed well), 2 tbsp onion powder, 1 tbsp paprika. Sometimes i also mix the exterior mix with a stick or two of butter.
Tie the roast back together and season the outside thoroughly. it’s best to have a rack for the roast so it’s not just sitting in the pan, my rack didnt fit so I used the metal wire frame from an aluminum roasting pan which worked perfect and its easier to get it out so you can make the Jus after you scrape all the good dark brown stuff into the juices. Add one cup thick sliced celery, one large yellow onion and one cup baby carrots in the pan with 1 1/2 cups beef broth
Place roast in the oven at 475 for 20 minutes then reduce the temp to 325 for the remainder of the cooking time, use a meat thermometer in the roast, preferably a digital probe so you can watch it and not have to keep opening the door and poking it letting the juices leak out. if you have more time do the opposite and cook on a grill / Smoker or in the oven at 250 and when the desired temp is reached (125 for rare 130 Med rare 135 Med) then transfer to an oven or other grill at least 475 degrees for 15 minutes if on a grill make sure to have a pan under it as described minus the veggies, do them in a separate pan, you want the juices
When the Roast has reached 125 for rare or to 132 to 135 for Med-Rare take it out and cover it with foil to rest for at “LEAST” a 1/2 hour otherwise all the juices will run and you’ll have a grey piece of dry meat, again if reverse cooking take it out and transfer to a hotter source for 15 minutes
after it has rested and your ready to serve, peel back the roast and separate it from the ribs (save those babies for an awesome munchie while watching the game) and carve away.
For the Jus, yes, its just “Jus” not Au Jus… Au means “with” and Jus is “Juice” so Prime Rib Au Jus is Prime rib with juice. scrape the drippings from the pan and I mean scrape…scraping the dark spots melts in the condensed flavors and make sure you keep all the veggies into a pot too…
strain the juice and seperate the fatty oil from the drippings (save fat for the yorkshire pudding) leave the veggies back in the pot and add 2 cups beef stock and one cup good red wine and simmer until reduced by 1/2 (about 15 minutes or so), strain juice and serve.