Preheat oven to 350°F Drain pears, reserving juice; set both aside. Combine melted butter, the 1/2 cup brown sugar, corn syrup, and 1 tablespoon reserved pear juice. Pour brown sugar mixture into a 10-inch round baking pan or a 10-inch ovenproof skillet.
Cut each pear half into a fan by making four or five lengthwise cuts starting 1/2 inch from the stem end of pear through the bottom. Arrange pears over syrup in pan with small ends to the center and rounded sides down. Set aside.
In a mixing bowl stir together flour, ginger, orange peel, cinnamon, baking powder, and baking soda. Set aside.
In a medium mixing bowl beat together the 1/3 cup butter and the 1/3 cup brown sugar with an electric mixer on medium to high speed until fluffy. Add egg and beat well. Beat in pumpkin and molasses until combined.
Alternately add flour mixture and 1/3 cup of the reserved pear juice to pumpkin mixture, beating at low speed after each addition just until smooth. Carefully spoon over pears in pan. Spread mixture evenly with back of spoon.
Bake for 30 to 35 minutes or until a wooden toothpick inserted near the center comes out clean. Cool cake in pan on a wire rack for 10 minutes. Using a narrow metal spatula, loosen cake from sides of pan. Carefully invert cake onto a serving plate. Serve warm, garnished with whipped cream. Cover and refrigerate any leftovers.
Makes 10 servings.