Preheat oven to 350°. Lightly spray bottom of a 13×9-inch baking pan with cooking spray. Line pan with parchment paper, letting excess extend over sides of pan.
For crust: In a large bowl, whisk together flour, confectioners’ sugar, and salt. Using a pastry blender or 2 forks, cut in cold butter until mixture is crumbly. Firmly press mixture into bottom of prepared pan.
Bake until golden brown, about 25 minutes. Leave oven on.
For filling: In a large bowl, whisk together sugar, buttermilk, melted butter, eggs, lemon zest and juice, cornmeal, flour, and vanilla until smooth. Pour filling into prepared crust.
Bake until filling is set, about 30 minutes. Let cool completely on a wire rack.
Using excess parchment as handles, remove from pan before cutting into squares. Garnish with confectioners’ sugar, if desired. Store in an airtight container for up to 3 days.
Notes
Be sure to give your carton of buttermilk a good shake before measuring; it will settle and separate over time.
Recipe by Paula Deen Magazine at https://pauladeenmagazine.com/buttermilk-chess-bars-recipe/