A food processor makes quick work of mincing the fresh ginger for this cake. (No, the amount of ginger is not a typo.)
Preheat the oven to 350°F. Grease and flour a 9-inch square baking pan and line the bottom with a square of parchment paper.
Whisk together thoroughly in a medium bowl:
Whisk together in a large bowl:
Combine in a medium saucepan and heat until the butter is melted:
Whisk into the molasses mixture. Stir the flour mixture into the molasses-butter mixture just until smooth. Scrape the batter into the pan. Bake until a toothpick inserted into the center comes out clean, 25 to 30 minutes.
Let cool in the pan on a rack for 10 minutes. Slide a thin knife around the cake to detach it from the pan. Invert the cake onto the rack, peel off the parchment paper, and turn right side up to cool completely. Serve dusted with: