How to Make It
Preheat oven to 350°F.
Weigh or lightly spoon flours into dry measuring cups; level with a knife. Whisk together flours, cinnamon, baking soda, and salt in a large bowl. Whisk together buttermilk, molasses, oil, beer, granulated sugar, ginger, and egg in a medium bowl; add to flour mixture, whisking just until blended.
Pour batter into an 8-inch square glass or ceramic baking dish coated with cooking spray. Bake 25 minutes or until a wooden pick inserted in center comes out clean. Cool 45 minutes in pan on a wire rack. Sprinkle gingerbread with powdered sugar; cut into 12 squares.