01 - Preheat oven to 350°F. Place unsalted butter in a 9x9 inch baking dish and melt in the oven for 3 to 4 minutes until fully liquified. Remove dish from oven.
02 - In a mixing bowl, whisk together all-purpose flour, baking powder, salt, and granulated sugar until thoroughly combined.
03 - Add buttermilk or whole milk, vanilla extract, and lemon extract (if using) to the dry mixture. Whisk until a smooth, lump-free batter forms.
04 - Pour the prepared batter evenly over the melted butter in the baking dish. Avoid stirring to maintain separate layers.
05 - Spoon lemon pie filling or lemon curd evenly over the surface of the batter.
06 - Bake in the center of the oven for 45 to 55 minutes until the top is puffed and golden brown at the edges.
07 - Remove from oven and allow to cool slightly. The lemon mixture will form a pudding-like layer at the bottom. Serve warm, optionally topped with whipped cream, ice cream, lemon slices, or powdered sugar.