[December 23, 2013 Update: This recipe was a finalist in the BEST DESSERT category of Safeway’s Tastier Holiday Recipe Contest, 2013. Thank you, voters and judges!]
Preheat your oven to 350F degrees. Coat a 6-cup Bundt pan with non-stick cooking spray.
Combine flours, pumpkin pie spice, baking powder, baking soda, and salt in medium bowl. Whisk to mix well. Combine butter and brown sugar in large bowl and beat at medium speed until mixed well. Beat in pumpkin and egg. Reduce to low speed and beat in flour mixture. Beat in buttermilk and 2 teaspoons vanilla, just until moistened. Pour batter into prepared pan.
Bake 25 to 30 minutes or until toothpick inserted comes out clean. Cool the cake in pan on wire rack for 10 minutes. Remove cake from pan and cool completely on wire rack.
Melt the bittersweet chocolate slowly in a microwave-safe bowl. Add the juice, a teaspoon at a time, while mixing well with a whisk. Drizzle over the cooled cake.