Preheat oven to 375 degrees.
Using 1 tablespoon butter, grease the skillet or baking dish. Be sure to cover the bottom and up the sides.
In a large bowl, whisk together the flour, baking powder, baking soda and salt.
In a separate bowl, beat the butter and granulated sugar with an electric mixer until fluffy. Add the egg and beat to combine.
Slowly add the flour mixture in 3 batches, alternating with the milk, beating until combined. Add the vanilla and sour cream beating for an additional 30 seconds.
Pour the batter into the prepared skillet or baking dish and arrange the peaches on top.
Sprinkle with turbinado sugar.
Transfer the skillet to the oven and bake for 40-45 minutes or until golden and cake tester comes out clean when inserted into the center of the cake.
Transfer to a wire rack and cool for 15-20 minutes before serving topped with ice cream, if desired.