Preheat the oven to 325°F (160°C).
Place the ham cut side down in a roasting pan, sprinkle with ½ cup of brown sugar (optional), and cover with foil.
Roast for 10-12 minutes per pound (1½-2 hours). Apply the glaze during the last 30 minutes.
For the glaze, combine brown sugar, mustard, orange juice, pineapple juice, honey, spices, rum, and lemon juice in a saucepan. Boil and simmer for 5 minutes until syrupy.
30 minutes before the ham is done, remove it from the oven, arrange pineapple rings on top, and secure cherries in the center of each ring.
Brush the ham with glaze and bake for 15-20 minutes, basting every 10 minutes until the internal temperature reaches 120°F.
Let the ham rest for 15 minutes before serving, and serve with extra glaze.