Place 1/2 cup butter in a 10-inch cast iron skillet. Place in cold oven; preheat oven to 350°F. Once butter has melted, whisk 1/3 cup brown sugar into melted butter in skillet. Arrange pears cut sides down in skillet. Roast 20 to 25 minutes or until just tender and starting to brown. Meanwhile, in a medium bowl whisk together flour, baking powder, ginger, salt, baking soda, nutmeg, and cloves.