**Preheat the Oven:** Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish and set aside.
**Make the Batter:**
- In a mixing bowl, whisk together flour, baking powder, salt, and sugar.
- Add melted butter, milk, and vanilla extract, and mix until smooth.
- Pour the batter evenly into the prepared baking dish.
**Prepare the Cinnamon Sugar Topping:**
- In a small bowl, combine brown sugar and cinnamon.
- Sprinkle the mixture evenly over the batter.
**Add the Syrup:** Carefully pour the boiling water over the entire mixture. Do not stir—the water will create the cobbler’s gooey base as it bakes.
**Bake:** Place the dish in the oven and bake for 40-45 minutes, or until the top is golden and the cobbler is bubbling around the edges.
**Cool and Serve:** Let the cobbler cool for 10 minutes before serving. Serve warm with a scoop of vanilla ice cream or a dollop of whipped cream.