If your ham is sealed in plastic, leave it sealed. If it is not sealed, put it in a large zipper-style plastic bag and seal. Submerge the sealed ham in a large bowl or sink filled with hot tap water. Let it sit for an hour, changing the water halfway through to assure that the water stays warm. You want the ham to be room temperature for even baking.
Heat the oven to 250°F. with the rack in the lowest position. Unwrap the ham and place cut side down on a large piece of heavy-duty aluminum foil, wrapping and sealing it securely so it will not leak. Place on a sturdy cookie pan, still cut side down, and bake until the internal temperature reaches about 110°, 8 minutes a pound or about 1 hour for a 7-pound ham. While the ham is baking, prepare the miso-and-apple glaze. m In a medium saucepan, combine the miso, apple butter, apple cider, grated apple, sugar and pepper. Place over medium heat and stir until the mixture is thick and bubbly, about 4 or 5 minutes. Remove from heat and set aside to cool.
When the ham reaches 110°, remove it from the oven. Raise the oven temperature to 450°. Pull the foil away from the top of the ham and brush the ham liberally with the glaze, allowing excess to drip to the bottom of the foil. Return the ham to the oven, with the foil still rolled back. Bake until the glaze forms a bubbly, sticky crust (about 10 minutes) or bake for 5 minutes and then put it under the broiler for a few minutes until the crust is slightly burnt.
Remove from the oven, tent loosely with foil and let it rest for 10 minutes before carving. Serve doused with the mixture of juices and glaze in the bottom of the foil.