Preheat your oven to 350°F. While it heats, place the butter in a baking dish and let it melt inside the oven.
In a medium bowl, whisk together flour, sugar, baking powder, salt, and cinnamon.
Stir in milk and vanilla extract until the batter comes together, smooth but not overmixed.
Pour the batter over the melted butter in the baking dish. Don’t stir. Trust me, the magic happens in the oven.
Top evenly with sliced peaches and berries. The fruit will sink a little and bubble up later.
Bake for 40–45 minutes until golden brown and the fruit juices are bubbling at the edges.
Let it cool slightly before serving. It pairs perfectly with a scoop of vanilla ice cream.