1. To make the caramel pear topping:Mist a 9-inch springform pan with non-stick spray.In a small bowl, stir the melted butter and brown sugar together.
2. Place the butter in a medium mixing bowl, and pour the boiling water over it. Allow to stand, stirring occasionally, until the butter is melted. Stir in the brown sugar, molasses, and egg until combined.
3. Add the flour, ginger, cinnamon, salt, baking powder, and baking soda, and stir together until incorporated.
4. Transfer the batter to the prepared pan, and bake for 40to 50 minutes, or until a tester inserted in the thickest part of the cake comes out clean or with a few moist crumbs. Cool for 10 to 20 minutes, then remove the sides of the springform and invert onto a serving platter.