Preheat oven to 350°F (175°C). Place the unbaked pie crust in a 9-inch pie dish and crimp the edges. Refrigerate while you prepare the filling.

In a large bowl, whisk together the granulated sugar, cornmeal, and salt until evenly combined.

Pour in the melted butter and whisk until smooth and well incorporated.

Add the eggs one at a time, whisking well after each addition until the mixture is smooth.

Stir in the buttermilk, vinegar, and vanilla extract until the filling is evenly combined. It will be thin and pourable.

Pour the filling into the prepared pie crust.

Bake for 40-45 minutes, or until the top is deep golden brown and the center has a very slight jiggle when the pan is gently shaken. Cover the crust edges with foil or a pie shield after 25 minutes to prevent over-browning.

Remove from the oven and let cool completely at room temperature for at least 2 hours before slicing. The filling will continue to set as it cools.