1. Preheat the oven to 350°. In a 10-inch cast-iron skillet, melt 4 tablespoons of the butter. Add the pears and cook over high heat, stirring, until crisp-tender. Add 4 tablespoons of the butter, the brown sugar and honey and stir over moderate heat until melted. Off the heat, arrange the pears in an overlapping ring, with the pointed ends facing the center. Fill the center with pears and sprinkle with the crystallized ginger.
2. In a medium bowl, whisk the flour, baking powder, cinnamon, ground ginger, nutmeg and salt. In a large bowl, cream the remaining stick of butter. Add the granulated sugar; beat until light and fluffy. Beat in the eggs, 1 at a time. Add the vanilla. Beat in the dry ingredients in 3 additions, alternating with the milk. Spoon the batter evenly over the pears, spreading it to the edge.
3. Bake the cake on the bottom oven rack for 30 minutes, or until golden and a toothpick inserted in the center comes out clean. Let cool for 10 minutes, then invert a plate over the skillet. Quickly invert the skillet to release the cake. Replace any pears that stick to the skillet and drizzle any remaining syrup over the cake. Let cool before serving.
Make Ahead: The unmolded cake can be refrigerated for up to 2 days.