Preheat your oven to 350°F (175°C). Pour the melted butter into a 9×13-inch baking dish, tilting the pan so the butter coats the entire bottom.

In a mixing bowl, whisk the milk, vanilla, and granulated sugar until smooth. Add the flour, baking powder, salt, and cinnamon and whisk just until combined into a slightly thick batter — don’t overmix.

Spoon the batter gently over the butter in the prepared pan. Spread carefully so the butter and batter remain mostly separate.

Scatter the packed brown sugar evenly across the top of the batter.

Slowly pour the hot water over the pan. Do not stir — the water will sink and mingle with the brown sugar during baking to create the luscious sauce.

Bake for 30–35 minutes, until the surface turns golden and the edges bubble. The center should be set but still tender beneath the crust.

While hot, mix the topping sugar and cinnamon together and sprinkle it across the warm cobbler.

Let it cool briefly, then serve warm. A scoop of vanilla ice cream or a dollop of whipped cream makes this extra decadent.