Step 1: Start by preheating your oven to 500 degrees Fahrenheit. This high temperature is crucial for creating that perfect crust.
Step 2: Next, take your 15-pound bone-in prime rib roast and use paper towels to pat off any excess moisture. Transferring it to a large roasting pan or baking dish ensures it has space to cook evenly.
Step 3: In a small bowl, combine 1 cup unsalted butter, 5 minced cloves of garlic, 1 teaspoon garlic powder, 1 tablespoon chopped fresh rosemary, 1 tablespoon chopped fresh thyme, and 1/2 teaspoon black pepper. Mix until well combined, creating that delicious garlic butter mixture.
Step 4: Rub this garlic butter mixture generously over the entire surface of the prime rib. Make sure to cover all sides, ensuring every bite will be flavorful.
Step 5: Now, stand your prime rib upright with the fat cap facing up. This positioning is crucial for the cooking process.
Step 6: Roast in the preheated oven at 500 degrees for 5 minutes per pound. For a 5-pound prime rib, this means about 25 minutes of roasting time to achieve that stunning crust.
Step 7: After roasting, you can open the oven door momentarily to let out some heat and then lower the oven temperature to 300 degrees F. This step is vital for slow-cooking the prime rib to perfection.
Step 8: Continue baking until the internal temperature reaches your desired level of doneness: 120 to 125 degrees F for rare, 130 to 135 degrees F for medium-rare, or 138 to 140 degrees F for medium. For medium-rare, this should take just under two hours for a 5-pound roast.
Step 9: To check the temperature accurately, insert an instant-read thermometer into the thickest part of the roast, avoiding the bone. Wait until the numbers stabilize for a precise reading.
Step 10: Once your roast reaches the desired temperature, pull it out of the oven and let it rest for at least 15 minutes. Resting is crucial as it allows the juices to redistribute throughout the meat.
Step 11: As the prime rib rests, consider preparing an au jus or gravy from the drippings in the bottom of the roasting pan. This will elevate your meal even further.
Step 12: Transfer the rested prime rib to a cutting board and use a sharp knife to slice it into steaks. If you have a bone-in rib roast, slice off the ribs prior to cutting it into steaks for easier serving.
Step 13: Finally, serve your Garlic Butter Prime Rib with your favorite side dishes, and enjoy the fruits of your labor!