Preheat oven to 350°F (175°C).
Pour the melted butter into a 9x13 inch ceramic or glass baking dish, spreading it evenly across the bottom.
In a medium mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt.
Stir in the milk until just combined and a smooth batter forms.
Pour the batter over the melted butter in the baking dish. Do not stir the batter into the butter.
Sprinkle the packed light brown sugar evenly over the batter layer, followed by the chopped pecans.
Carefully pour the boiling water over the top of the pecan and sugar layer. Do not stir; the layers will integrate during the baking process.
Bake for 40 to 45 minutes until the top is golden brown and the cake has risen through the liquid to create a cobbler crust.
Remove from the oven and allow to rest for 10 to 15 minutes to allow the sauce to thicken before serving.