Preheat your oven to 350°F (175°C). This ensures that your bars bake evenly and thoroughly.
In a medium mixing bowl, whisk together the all-purpose flour, confectioners' sugar, and salt. Add the cold, cubed salted butter. Using a pastry cutter or your fingers, mix until the mixture resembles coarse crumbs.
Transfer the crumbly mixture into the 9x13-inch baking dish. Press it down firmly and evenly across the bottom to form a crust. Bake in the preheated oven for about 15-20 minutes, or until lightly golden.
While the crust is baking, prepare the filling. In a large mixing bowl, combine the granulated sugar, whole buttermilk, melted salted butter, eggs, lemon zest, lemon juice, cornmeal, all-purpose flour, and vanilla extract. Whisk until smooth and well combined.
Once the crust is baked, remove it from the oven and pour the filling mixture over the hot crust. Spread it evenly with a spatula.
Return the baking dish to the oven and bake for an additional 25-30 minutes, or until the filling is set and slightly golden on top. The bars should jiggle slightly in the center when done.
Remove the bars from the oven and allow them to cool completely in the pan. Once cool, cut into squares and serve. For an extra touch, dust the tops with additional confectioners' sugar before serving.
