Preheat the oven to 350°F (177° C). Spray your muffin pan with non-stick cooking spray.

In a small bowl, combine cold butter and brown sugar until blended but crumbly.

Peel and slice the peaches into thin wedges.

Place 2 teaspoons of the brown sugar mixture in the bottom of each muffin cup and layer peach slices on top.

In a large bowl, whisk together flour, baking powder, baking soda, and salt.

In another bowl, cream the room-temperature butter and granulated sugar until fluffy, then add the egg and vanilla extract.

Alternately mix the dry ingredients and buttermilk into the butter mixture.

Spoon the batter over the peach topping, filling each cup about two-thirds full.

Bake for 20-25 minutes until a toothpick inserted in the center comes out clean.

Let cool slightly before flipping out onto a wire rack.