Preparation

• Position a rack in the center of the oven and heat the oven to 350°F. Spray a 10- to 12-cup Bundt or tube pan with cooking spray, then dust with flour.
• In a medium bowl, whisk the flour, baking powder, 1-1/2 tsp. of the ginger, the nutmeg, baking soda, and salt. In a small bowl or measuring cup, combine the milk and vanilla.
• In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and sugars on medium-low speed until light and fluffy, 3 to 4 minutes. Add the eggs one at a time, beating well after each addition and scraping down the bowl as needed. Add the sweet potatoes, and mix until the batter is combined. (it may look curdled at this point.) Stop the mixer and scrape down the bowl.
• With the mixer on low speed, add half of the flour mixture, and mix until just incorporated. Add half of the milk mixture, and beat on low until well blended, scraping down the bowl as needed. Repeat with the remaining flour and milk, beating on low until the batter is thick and smooth.
• Scrape the batter into the prepared pan, and spread it evenly. Bake until the cake springs back when pressed lightly and a wooden skewer inserted in the center comes out clean, 55 to 65 minutes. cool the cake in the pan on a wire rack for 20 minutes. Run a thin knife around the edge to loosen the cake if the pan shape allows, and then carefully invert it onto a rack to cool completely.
• Combine the confectioners’ sugar and the remaining 1/4 tsp. ginger. Use a medium fine-mesh sieve to dust the top of the cake with the sugar mixture. Serve immediately, or keep wrapped at room temperature