Simmer pear halves and brandy in a saucepan for 20 minutes over medium heat. In a separate saucepan, combine sugar, zest, and orange juice. Set aside. When pears are soft, transfer to a blender and puree*. Add puree to saucepan and simmer for 1 1/2 hours over low heat, stirring occasionally. Pear butter is ready when all the liquid has evaporated and the consistency is very thick. If canning, follow USDA guidelines for canning.
*When blending hot liquids: Remove liquid from the heat and allow to cool for at least 5 minutes. Transfer liquid to a blender or food processor and fill it no more than halfway. If using a blender, release one corner of the lid. This prevents the vacuum effect that creates heat explosions. Place a towel over the top of the machine, pulse a few times then process on high speed until smooth.