A cross between a cake-like cobbler and a traditional fruit crumble, a buckle is the perfect way to showcase juicy summer peaches.
Preheat oven to 350 degrees.
Melt butter in a 10-inch cast-iron skillet, preferably enameled, over medium heat.
Meanwhile, place peaches in a large bowl and sprinkle with 2 tablespoons granulated sugar.
In another large bowl, whisk together flour, baking powder, and salt. Add remaining 1 cup granulated sugar, milk, and vanilla; whisk until well combined. Whisk in melted butter. Pour mixture into skillet and top with peaches. Sprinkle with sanding sugar.
Bake until top is golden brown and a tester inserted in center comes out clean, 50 to 55 minutes. Serve warm or at room temperature with whipped cream, creme fraiche, or ice cream, if desired.