Preheat the oven: Preheat your oven to 350°F (175°C). Grease a 9×9-inch baking dish with butter or non-stick spray.

Prepare the batter: In a medium mixing bowl, whisk together the melted butter, whole milk, and vanilla extract until smooth. Stir in the sugar, flour, baking powder, salt, and cinnamon until well combined. Pour the batter into the prepared baking dish.

Add the brown sugar mixture: In a separate bowl, combine the brown sugar and hot water. Stir until the sugar is dissolved. Pour the brown sugar mixture evenly over the batter in the baking dish (do not stir).

Bake: Place the dish in the oven and bake for 45-50 minutes, or until the cobbler is golden brown and the top is firm. The dessert will have a gooey, caramel-like sauce at the bottom.

Prepare the topping: While the cobbler is baking, combine 1/4 cup sugar and 1/2 teaspoon cinnamon in a small bowl.

Finish the cobbler: When the cobbler is done baking, remove it from the oven and sprinkle the cinnamon-sugar topping over the hot cobbler.

Serve: Let the cobbler sit for a few minutes before serving. Serve warm with vanilla ice cream or whipped cream for an extra indulgence.