Back when I first tried my hand at making prime rib, I did a LOT of research to find a foolproof method. This is the method I ended up using, and I’ve been making it every Christmas ever since!
Mix up 1 tablespoon + 1 teaspoon each of onion salt, seasoned salt, and garlic powder, for a total of 1/4 cup of seasoning mix.
Pat the seasoning mix on both ends of the roast as well as the fat side. (The salt may not stick as well on the fat side, but don’t worry about it.)
Preheat the oven to 500°F.
Set the seasoned roast on a roasting rack, bone-side down and fat-side up. Place the rack in a large roasting pan, and insert your meat thermometer into the middle of the roast.
Then shut the oven off completely, and DO NOT OPEN THE OVEN DOOR FOR TWO HOURS.
After two hours, check the temperature of the meat. If your thermometer reads 135-140°F, it’s done! (If it isn't quite to temp yet, just put it back in the oven at 375°F until it's done.)
1 dash Tobasco hot pepper sauce (optional)
Whisk the cream in a mixing bowl until it forms stiff peaks.
Season with the white pepper, hot sauce, and horseradish.
Stir gently until just combined, and serve alongside your delicious prime rib!