Preheat the oven to 350º F (175º C).
Place the 6 tablespoons of butter in a 9×13-inch baking dish and place the dish in the oven to melt the butter.
Sprinkle the chopped pecans over the melted butter and set the baking dish aside.
In a large bowl, whisk together the self-rising flour, sugar, whole milk, and vanilla extract until the mixture comes together.
Pour the batter over the pecans in the baking dish, spreading it gently into an even layer. Do not mix the pecans into the batter once it has been poured into the baking dish.
Sprinkle the brown sugar in an even layer on top of the batter, without mixing.
Carefully pour the hot water on top of the brown sugar.
Place the baking dish in the oven and bake for 30-35 minutes, or until the cake is golden brown.
Remove the baking dish from the oven and let it cool for at least 15 minutes before serving.
Notes:
