Active Time

　　20 minutes

　　Total Time

　　6 hours

　　Just like the steakhouse-style prime roast your grandparents served at Christmas, but better, because it’s made using the reverse-sear method for a super-tender, evenly cooked interior and an extra-crispy crust.

　　

Ingredients

8–10 servings

　　1 (6-pound) boneless prime rib roast, trimmed, tied

　　4 tablespoons store-bought or homemade Montreal-style steak seasoning, divided

　　1 cup sour cream

　　1/4 cup prepared horseradish

　　1 teaspoon freshly ground black pepper

　　1/2 teaspoon kosher salt

　　1/2 cup Dijon mustard, divided

　　1/4 cup (1/2 stick) melted unsalted butter

　　

Step 1

Season roast all over with 2 Tbsp. steak seasoning. Transfer to a wire rack set inside a rimmed baking sheet and let sit at room temperature 1 hour.

　　

Step 2

Preheat oven to 225°F. Roast beef until an instant-read thermometer inserted into the center registers 120°F, 3 1/2–4 hours (start checking every 5–10 minutes after 3 1/2 hours). Tent with foil and let sit at least 30 minutes and up to 1 hour. Increase oven temperature to 500°F.

　　

Step 3

Meanwhile, whisk sour cream, horseradish, pepper, salt, and 1/4 cup mustard in a small bowl; set aside.

　　

Step 4

Remove string from roast; discard. Stir butter and remaining 1/4 cup mustard in another small bowl. Using a pastry brush, thickly coat roast with mustard-butter sauce. Coat with remaining 2 Tbsp. steak seasoning. Roast beef until a brown crust forms, 5-10 minutes. Transfer to a cutting board and carve. Serve with sour cream sauce alongside.

　　

Do Ahead

Step 5

Sour cream sauce can be made 1 day ahead. Transfer to an airtight container and chill.