Preheat the oven to 350°F and grease a 9x13-inch baking dish.
In a large mixing bowl, whisk together the flour, brown sugar, baking powder, salt, and cinnamon. Add in the milk, vanilla extract, and melted butter, stirring until a smooth batter forms.
Pour the batter into the prepared baking dish and spread it evenly across the bottom.
In a separate bowl, combine the pecans and brown sugar. Stir in the hot water until the mixture is evenly coated and sticky.
Spoon the pecan topping evenly over the cobbler batter, drizzling leftover syrup over top.
Bake for 40 to 50 minutes, or until the cobbler is set and the top is golden brown.
Let cool slightly before serving. Serve warm with whipped cream or vanilla ice cream, if desired.