Preheat the oven to 350 degrees. Prepare a 9 inch cake pan with nonstick cooking spray. Then, add a layer of parchment cut into a circle.

In a small bowl, mix together the brown sugar and melted butter. Spread the mixture over the parchment paper. Arrange the sliced peaches over the brown sugar mixture.

Meanwhile, in a large mixing bowl, beat the butter and sugar together until light and fluffy, scraping down the sides often, about 6 minutes.

To the sugar mixture, add the egg and vanilla, mixing well.

In a small bowl, whisk together the flour, baking powder, and salt. Blend the flour mixture into the batter a scoop at a time, alternating with the milk, until well mixed.

Transfer the batter to the cake pan and spoon evenly over the peaches.

Bake for 50 to 55 minutes or until a toothpick inserted in the center returns clean.

Place the cake pan on a wire rack to cool for 10 minutes.

Run a knife around the edge and then place a plate over the cake and invert it onto the plate.

Carefully lift the parchment paper off the peaches, replacing any peaches that stick.

Allow the cake to cool completely or serve slightly warm.