Brown roast on all sides in oil in a large skillet. Place roast, fat side down, on rack in a shallow roasting pan. Sprinkle with salt and pepper. Insert meat thermometer, if desired.
Bake, uncovered, at 375° until desired degree of doneness: about 1 hour or 140° (rare), about 1 hour and 10 minutes or 160° (medium).
Transfer roast to a warm platter; let stand 10 minutes before slicing. Reserve pan drippings.
Combine drippings and flour in a saucepan. Cook over medium heat, stirring constantly, until smooth. Gradually add whipping cream, stirring well. Set aside and keep warm.
Place Cognac in a small saucepan; heat just until warm. Ignite with a long match, and pour over roast. Slice roast and serve with sauce after flames die down.
Oxmoor House Homestyle Recipes