How to Make It
Heat oven to 350° F. Rub an 8-inch square cake pan with the butter. Sprinkle the bottom of the pan with the brown sugar and top with the peaches.
Combine the flour, granulated sugar, baking powder, cinnamon, baking soda, and salt in a medium bowl. In a separate bowl, whisk together the buttermilk, eggs, oil, and vanilla. Add the wet ingredients to the dry ingredients and whisk to combine.
Pour the batter over the fruit and tap the bottom of the pan on the table to remove any air bubbles. Bake until a toothpick inserted in the center of the cake comes out clean, 35 to 45 minutes. Cool in the pan for 5 minutes. Run a knife around the outside of the cake to loosen; turn out onto a wire rack to cool completely.