Preheat your oven to 350°F (175°C) and melt ¼ cup of unsalted butter in a 9-inch glass baking dish until bubbly, about 5 minutes.

In a bowl, whisk together ½ cup flour, ⅔ cup granulated sugar, 1 teaspoon baking powder, and ¼ teaspoon salt until well combined.

Add ⅓ cup milk and 1 large egg to the dry mixture, stirring gently until just combined.

Pour the batter into the baking dish over the melted butter, without stirring.

In another bowl, combine 2 cups peaches, ⅓ cup sugar, ¼ teaspoon vanilla, ½ teaspoon cinnamon, and ¼ teaspoon nutmeg. Mix gently.

Spoon the peach mixture over the batter carefully.

Sprinkle ¼ cup brown sugar over the peach mixture.

Bake for 40-45 minutes until golden brown and bubbly. For extra crispness, broil for a minute or two.

Allow to cool slightly for about 10 minutes before serving.