Preheat your oven to 350°F (175°C). Position a rack in the center of your oven.
Place your pie crust in a 9-inch pie plate, crimp the edges decoratively, and prick the bottom several times with a fork.
For protection against a soggy bottom, blind bake the crust for 10 minutes with pie weights, then remove the weights and bake for 5 more minutes until just starting to color.
In a medium bowl, whisk together the sugar, flour, cornmeal, and salt until well combined.
In a large bowl, lightly beat the eggs, then add the melted butter, buttermilk, vanilla extract, lemon juice, and lemon zest if using. Whisk until smooth and fully incorporated.
Gradually add the dry ingredient mixture to the wet ingredients, whisking continuously to prevent lumps. Continue whisking until the mixture is smooth and silky.
Pour the filling into your prepared pie crust. To prevent spillover, place the pie plate on a baking sheet before carefully transferring to the preheated oven.
Bake for 45-50 minutes until the top is golden brown and slightly cracked, with a center that jiggles only slightly when gently shaken.
Remove the pie from the oven and allow it to cool completely on a wire rack for at least 3 hours. For the best texture and flavor development, refrigerate overnight.