Preheat and Prepare:Preheat your oven to 350°F (175°C). Lightly grease an 8x8-inch baking dish or a similarly sized casserole dish.
Make the Base:In a medium bowl, whisk together the flour, baking powder, salt, and granulated sugar. Stir in the milk, melted butter, and vanilla extract until combined. Pour the batter into the prepared baking dish and spread it evenly.
Add the Topping:In a separate bowl, mix together the brown sugar and cinnamon. Sprinkle the mixture evenly over the batter.
Pour the Liquid Mixture:Slowly and evenly pour the hot water over the top. Do not stir; the water will form a gooey, caramel-like sauce as the cobbler bakes.
Bake:Place the dish in the oven and bake for 40–45 minutes, or until the top is golden brown and bubbly.
Cool and Serve:Let the cobbler cool slightly before serving. Enjoy it warm with vanilla ice cream or whipped cream for the ultimate dessert experience.