Preheat your oven to a cozy 325°F (160°C) and adjust the oven rack to the lower-middle position. Line a sturdy roasting pan or baking sheet with foil, and give the metal rack insert a light coat of cooking spray. Unwrap your ham, removing any plastic caps, and place it flat-side down on the prepared rack.
In a small bowl, whisk together the melted unsalted butter, honey mustard, pure honey, and whole grain mustard until you have a smooth, delicious glaze.
Generously rub this tempting honey glaze all over the ham, making sure it seeps in between the slices for maximum flavor. Pour the natural apple cider into the bottom of the roasting pan. Cover the ham and pan tightly with aluminum foil. Bake for 2 to 3 hours (about 20 minutes per pound) or until an instant-read food thermometer nestled in the thickest part reads 140°F (60°C). Take the ham out of the oven and let it cool for about 15 minutes.
While your ham is cooling, grab a medium bowl and whisk together all the dry rub ingredients: granulated sugar, fine sea salt, ground nutmeg, ground cloves, ground cinnamon, ground ginger, ground allspice, and sweet paprika. Set aside half of this magical mixture in a small saucepan – this will be for your amazing serving glaze later!
After the ham has cooled for 15 minutes, uncover it and brush it all over with the flavorful pan juices. Now, press the remaining dry rub mixture all around the ham, a handful at a time, until it's fully coated. To achieve that signature crunchy, caramelized crust, you have two options: Kitchen Torch: Hold the torch flame about an inch away from the ham, moving it continuously in small circles until the surface becomes bubbly and beautifully caramelized. Repeat until the entire ham is glistening. Broiler Method: If using your oven's broiler, adjust the rack to the lowest position. Watch the ham extremely closely, turning it often to prevent any burning, until it develops a gorgeous, sugary, crispy coat. Loosely cover the ham with foil and set it aside until you're ready to serve.
Add the remaining pan juices to the dry rub mixture you saved in the saucepan. Bring this mixture to a boil over medium heat, stirring frequently. Once boiling, reduce the temperature to medium-low and let it simmer for 4-6 minutes, or until it reduces into a thin, syrupy glaze. Remove from heat. If the glaze starts to firm up before serving, just warm it gently over very low heat.
When it's time to feast, slice your magnificent ham and drizzle generously with the warm, syrupy glaze. Enjoy your wholesome homemade Christmas ham!