Preheat oven to 350°F. Grease a 9-inch springform pan with cooking spray. Set aside.
In a large bowl, stir together flour, sugar, whole wheat flour, cornmeal, ginger, cinnamon, nutmeg, and pepper.
Using a pastry cutter or two forks, cut in butter until mixture resembles coarse crumbs. Remove ¾ cup of crumb mixture for topping and set aside.
In a medium bowl, combine eggs, pumpkin, molasses, buttermilk, and baking soda.
Add pumpkin mixture to crumb mixture in large bowl. Stir until just moistened.
Spread batter into prepared pan. Sprinkle with reserved ¾ cup crumb mixture.
Bake for 55-60 minutes, or until a toothpick inserted into center of cake comes out clean. Cool in pan on a wire rack for 30 minutes.