Mustard-Crusted Boneless Prime Rib Roast with Cream Sauce

A luxurious prime rib roast encrusted with mustard and Montreal steak seasoning, slow-roasted to perfection and served with a creamy horseradish sauce. This impressive main dish is perfect for special occasions.

8 servings
5 hr 20 min

Ingredients

  • 1 piece boneless prime rib roast
  • 4 tablespoons Montreal-style steak seasoning
  • 1 cup sour cream
  • ¼ cup prepared horseradish
  • 1 teaspoon freshly ground black pepper
  • ½ teaspoon kosher salt
  • ½ cup Dijon mustard
  • ¼ cup unsalted butter

Cooking Instructions

  1. 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.

    60 min

  2. 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.

    240 min

  3. 3.

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

    5 min

  4. 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.

    10 min

  5. 5.

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

    5 min