How to Make It
Combine cranberries, 1/2 cup water, sugar, vinegar, zest and salt in a large pan. Bring to a boil. Reduce heat to medium-low; simmer until berries have burst, about 10 minutes. Strain into a large bowl, pressing against solids to extract as much liquid as possible (you should have about 2/3 cup). Discard solids.
Melt butter over medium-high heat in a skillet large enough to hold ham flat. Pat ham dry and cook until lightly browned, about 5 minutes per side. Transfer to a large plate and pour off all but 1 Tbsp. liquid in skillet.
Pour strained cranberry mixture into skillet, add 1 Tbsp. water and stir over low heat until smooth, scraping up any browned bits from bottom of skillet. Whisk in mustard. Return ham to skillet and turn a few times to coat and warm through. Transfer to a platter and drizzle with any extra glaze. Serve warm.