This dish is a definite showstopper, but it only takes a few ingredients to prepare. To ensure exquisite results, buy the best ingredients you can find. Look for guava nectar in the juice aisle of your grocery store.
Preheat oven to 325°F. Line a roasting pan with foil, top with a shallow rack, and set aside.
Use a sharp knife to remove the rind of the ham, leaving the layer of fat intact. Score a 1-inch wide diamond pattern through the fat (no more than ¼-inch deep) and over the entire ham. Transfer to rack in the prepared pan and pour in ½ cup water.
Bake, uncovered, for 1 hour.
Meanwhile, melt butter in a medium saucepan over medium heat. Add ginger and cook until fragrant, about 30 seconds. Stir in guava nectar, honey, lime juice, dark rum, ½ teaspoon salt and black pepper to taste. Bring to a boil, reduce to a simmer and cook, stirring occasionally, until mixture is slightly syrupy, about 20 minutes. Set aside.
After ham has baked for 1 hour, brush the surface with guava glaze.
Bake for an additional 1 hour 30 minutes, brushing ham with glaze every 10 minutes. Remove from oven and let rest 15 minutes before carving.