4 tablespoons unsalted butter, at room temperature, plus more for the dish
1 2/3 cups all-purpose flour
1 1/2 teaspoons baking powder
1/4 teaspoon salt
3/4 cup granulated sugar
1/4 teaspoon finely grated orange zest
1 large egg
1/2 cup milk
2 cups blueberries
1 large peach, chopped
1/4 cup granulated sugar
2 tablespoons packed light brown sugar
3 tablespoons all-purpose flour
1/4 teaspoon freshly grated nutmeg
Pinch of salt
2 tablespoons unsalted butter, at room temperature
Vanilla ice cream, for serving