Preheat oven to 350°F.
Melt butter: Place butter in a 11 x 7 inch baking dish and melt it in the oven.
Add pecans: Once butter is melted, sprinkle 1 cup of pecans evenly over it.
Make the batter: In a medium bowl, mix together flour, salt, baking powder, sugar, milk, and vanilla until just combined.
Pour the batter over the melted butter and pecans. Do not stir.
Add topping: Sprinkle the brown sugar and chopped pecans evenly over the batter.
Finish with hot water: Slowly pour the very hot water over everything—do not stir.
Bake for 25–30 minutes, or until the top is golden and bubbly.
Cool slightly before serving to allow the sauce underneath to thicken.
