Preheat the oven to 350°F. Line 24 muffin cups with paper liners.
In a large bowl, whisk together the cake flour, baking powder, baking soda and salt.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter, granulated sugar and brown sugar. Add the eggs one at a time, mixing until combined, then add the vanilla and sour cream.
Stir the dry ingredients into the wet and then gently fold in the diced peaches.
Scoop the batter into the prepared muffin tins and bake for until a toothpick comes out clean, 18 to 22 minutes.
Allow the cupcakes to cool in the muffin tins for 5 minutes, then transfer them to a wire rack and allow them to completely cool while you make the frosting.