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1
Prepare the ham
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2
Set the ham fat side up in a large heavy-duty roasting pan. Use a sharp knife to score the fat in a 1-inch diamond pattern, cutting only about three-quarters of the way through the fat.
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3
Peel the zest from the lemon with a vegetable peeler, avoiding the white pith. Put the zest, olive oil, rosemary, garlic, 1 Tbs. salt, and 1 tsp. pepper in a food processor and pulse to a coarse paste. Rub this mixture all over the ham. Cover the pan tightly with foil and refrigerate for 12 to 24 hours.
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4
Position a rack in the oven so that the ham will sit as high as possible but still have at least 2 inches head space for air circulation. Heat the oven to 350u00b0F.
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5
Keep the ham covered with the foil and roast for 3 hours. Uncover the pan and drizzle the vinegar over the ham, taking care not to wash off the coating. Continue roasting, basting every 15 minutes or so, until the ham is well browned and an instant-read thermometer inserted in the center of the meat without touching bone registers 170u00b0F (check in several places), 1 to 1-1/2 hours more. If the ham or drippings begin to brown too much, cover loosely with foil to prevent burning. Transfer the ham to a carving board to rest while you make the sauce.
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6
Make the sauce
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7
Pour the pan drippings into a bowl, let sit until the fat rises to the top, and then skim off the fat. Return the skimmed drippings to the roasting pan and set the pan over medium heat. Whisk in the wine, scraping up any 1/2 cup water, and continue to boil until the liquid is reduced by one-third, about 2 minutes. Meanwhile, use a fork to mash the butter with the flour in a small bowl or ramekin to create a thick paste. Whisk the cherry jam into the sauce, then add the butter paste in parts, whisking until the paste is fully dissolved and the sauce is simmering and thickened.
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8
Carve the ham and serve with the sauce. Leftover ham will keep in the refrigerator for up to 3 days and in the freezer for up to 2 months.
