Make topping: Peel, quarter and core pears. Toss with lemon juice. In a 9-inch skillet, melt butter and sugar. Add pears; cook until tips look translucent, about 8 minutes. Let cool.
Preheat oven to 350°F. Wrap outside of 6- or 7-inch springform pan in foil; grease inside. Arrange pears in pan and pour skillet syrup on top. Let cool.
Prepare batter: Sift together flour, ginger, baking powder, baking soda, cinnamon, salt and cloves. Set aside. In a bowl, beat sugar and egg until fluffy and thick, about 4 minutes. Mix in molasses and melted butter. Add half of dry ingredients, sour cream and then rest of dry ingredients just until smooth. Scrape batter into pan on top of cooled pears.
Bake 50 to 60 minutes, until springy. Let cool for 2 minutes, then invert a platter on top of skillet and flip to unmold.