Place the ham, cut side down, in a 13x9 inch baking dish. Cover with foil. Bake for 1 hour.
While the ham is baking, stir together the brown sugar and dijon mustard.
Remove the ham from the oven and remove the foil. Increase the oven temperature to 350°F.
Brush the brown sugar mixture over the ham.
Place back in the oven, uncovered, for 30 minutes, or until the glaze is sticky and the ham is warmed through.
Turn the ham on its side and run a knife along the circular bone in the middle. This will help release the slices from the ham nicely.
Serve warm or at room temperature.
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Notes
Making this recipe with a whole ham? Increase the brown sugar and dijon mustard to ¾ cup each. If you're making this with an unsliced ham, score the ham on the top in a diagonal pattern, about ½-inch deep, before brushing on the glaze. You can use light brown sugar instead of dark brown sugar, if you'd like. The ham can be served while warm, at room temperature, or cold. Leftover ham can be refrigerated and enjoyed within 5 days. You can also freeze ham for up to 3 months.