Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan and line the bottom with parchment paper.

Peel and slice the peaches. Set them aside on a paper towel to absorb any extra moisture.

In a medium bowl, whisk together the flour, baking powder, and salt.

In a separate large bowl, whisk together the melted butter and sugar. Add the egg and vanilla and mix until smooth. Pour in the buttermilk and stir well.

Add the dry ingredients to the wet and mix until just combined — don’t overmix. The batter will be thick.

Spread the batter into the prepared pan. Gently press the peach slices into the top in a single layer — they’ll sink slightly as the cake bakes. Sprinkle with sparkling sugar.

Bake for 40–45 minutes, or until a toothpick inserted in the center comes out clean. The top should be golden and the edges slightly crisp.

Let the cake cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely. Slice and serve!