Chocolate Potato Cake

1/3 cup unsweetened cocoa powder
1 cup all-purpose flour
1/2 teaspoon baking powder
1 cup sugar
1/2 cup canola oil
2 large eggs
1/2 cup cold, plain, mashed potatoes
1/2 teaspoon cinnamon
1/4 teaspoon baking soda
Pinch nutmeg
1/2 cup buttermilk
Pinch salt
Confectioner's sugar, for dusting cake

Preheat oven to 350°F. Lightly oil a 9-inch round cake pan and line the base with wax or parchment paper.

Whisk together sugar, oil and eggs in a large mixing bowl. Whisk in potatoes. Stir together flour, cocoa, baking powder, cinnamon, baking soda, nutmeg and salt in another bowl. Alternately add the dry ingredients and the buttermilk to the egg mixture, beginning and ending with the dry ingredients and stirring with a spoon or rubber spatula.

Spoon the batter into the prepared pan. Bake until the top springs back when touched lightly, 30 to 35 minutes. Let cool on a rack for 10 minutes. Invert the cake onto a rack and let cool thoroughly. Transfer to a plate and sift confectioners’ sugar over top.