Preheat oven to 450°F
Pat the prime rib dry
Season all over with salt, black pepper, and garlic powder
Place the roast fat-side up in a roasting pan
Roast for 15 minutes
Reduce oven temperature to 325°F
Continue roasting until internal temperature reaches:
120°F to 125°F for rare
130°F to 135°F for medium-rare
140°F to 145°F for medium
Remove from oven
Tent loosely with foil
Rest for 20 to 30 minutes
Slice against the grain
Serve immediately