Preheat oven to 400°. Spray a 10-inch cast-iron skillet with cooking spray.
In a medium bowl, stir together peaches, ½ cup granulated sugar, and cornstarch.
In a large bowl, whisk together buttermilk, melted butter, and eggs. In another large bowl, whisk together flour, cornmeal, baking powder, ginger, and remaining 1½ cups granulated sugar. Stir flour mixture into buttermilk mixture until combined. (Batter will be thick.) Spread batter into prepared pan. Place peaches on top of batter, leaving a ½-inch border. Pour remaining juices onto peaches.
Bake for 10 minutes. Cover with foil, and continue baking until a wooden pick inserted in center comes out clean, 45 to 55 minutes more. Let cool completely on a wire rack. Garnish with confectioners’ sugar, if desired.
Recipe by Southern Cast Iron at https://southerncastiron.com/peach-buttermilk-cake/