Horseradish Sauce: Whip the cream until stiff. Stir in the horseradish, lemon juice and salt. Cover and refrigerate for 1 hour thoroughly coat the beef with salt and pepper. Beef: Place the beef tenderloin on the Spit Rods. Rotate for 30 to 40 minutes or until the internal temperature reaches 140 degrees F for rare on the meat thermometer. Remove roast and slice into 1/2-inch thick slices and serve with Horseradish Sauce. Serves 6.