Preheat your oven to 350°F (175°C).
Grease a baking dish with butter or cooking spray.
Melt half a cup of butter in your prepared baking dish in your preheated oven.
In a mixing bowl, combine flour, baking powder, salt, and sugar. Whisk together until fully blended.
In another bowl, mix together buttermilk and vanilla extract. Gradually add this mixture into your dry ingredients until just combined.
Pour your prepared batter over melted butter in your baking dish without stirring, then spoon in your lemon pie filling.