Place onions in bottom of a 13x9 inch roasting pan. Rub surface of roast with desired amount of pepper. Place meaty side down on rack on top of onions. Roast at 325F until desired doneness, basting with beef broth every 30 minutes.
Remove from pan. Let stand 10 minutes before carving. Keep warm.
Meanwhile, place roasting pan on range top. Stir brown sugar, margarine, and nutmeg into onions. Cook over low heat until margarine is melted, about 5 to 10 minutes. Carve roast. Arrange slices on platter. Ladle onion sauce on top.
Cajun Country -- New Iberia, Louisiana