Preheat your oven to 350°F (175°C). In a small saucepan over low heat, melt the butter and brown sugar until smooth and bubbly, about 3-5 minutes. Spoon the caramel into greased muffin cups and layer peach slices on top.

In a mixing bowl, cream together the softened butter and granulated sugar until pale and fluffy, about 3-4 minutes. Add eggs one at a time, mixing well after each addition. Mix in vanilla extract.

Whisk together the flour, baking powder, and salt in a separate bowl. Gradually add this to the buttery mixture alternating with milk, starting and ending with dry ingredients until just combined.

Spoon the cake batter over the prepared peaches, smoothing the tops. Bake for 22-27 minutes until golden brown and a toothpick comes out clean.

Allow the cakes to cool for about 5 minutes, then run a knife around the edges to loosen and invert onto serving plates.