Preheat the oven to 250°F. Place the spiral ham in a large roasting pan and let it sit at room temperature for 30–45 minutes while you prepare the glaze.

In a medium saucepan, combine the brandy, cranberries, brown sugar, butter, and allspice. Bring to a gentle simmer over medium-low heat.

Cook the glaze for 15–20 minutes, stirring occasionally, until the cranberries burst and the sauce thickens slightly. The glaze should coat the back of a spoon but still be pourable.

For a smooth glaze, strain out the cranberry solids. For a thicker, more rustic texture, lightly blend the glaze using an immersion blender.

Cover the ham loosely with foil and bake for 30 minutes. Remove from the oven and brush generously with the cranberry brandy glaze.

Continue baking the ham for 1½–2 hours, brushing with more glaze every 10–15 minutes. Remove the foil for the last 20–30 minutes so the glaze can caramelize and form a glossy coating.

The ham is done when the internal temperature reaches 140°F.

Remove from the oven and let the ham rest for 15–20 minutes before slicing.

To make extra sauce, add a splash of water or brandy to the roasting pan and stir to loosen any caramelized bits. Spoon this over the sliced ham for added flavor.