Preheat your oven to 350°F (175°C) and place a rack in the middle position.

In a small saucepan over low heat, melt 3 tablespoons of butter and stir in the brown sugar until fully dissolved.

Spoon a tablespoon of the butter-sugar mixture into each cavity of a 6-cup muffin tin.

Arrange one peach wedge on top of the sugar mixture in each cup.

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

In another bowl, beat the egg lightly, then stir in the milk, melted butter, and vanilla extract.

Pour the wet ingredients into the dry mix and gently stir until just combined.

Divide the batter evenly among the muffin cups.

Bake for 18 to 20 minutes, or until a toothpick inserted in the center comes out clean.

Let the cupcakes rest in the tin for 5 minutes, then run a knife around the edges and gently invert onto a serving platter.