make the pie crust:Whisk together the flour, sugar, and salt in a medium bowl. Cut the cold butter into cubes and add it to the bowl. Using a pastry cutter, cut the cold butter into the flour mixture until well combined and the mixture resembles small crumbs. Make a well in the mixture, pour in the buttermilk, and stir with a fork until a dough forms and the entire mixture is moistened.

Place the dough on a lightly-floured surface and gently knead it into a disk. Wrap the dough in plastic wrap and refrigerate for 1 hour.

Remove the dough from the refrigerator and place it on a well-floured surface. Roll the dough into a circle that's about 12 inches in diameter and ⅛ inch thick. Transfer the dough to a 9-inch pie plate and crimp or press the edges. Cover the crust with plastic wrap and return to the refrigerator for 30 minutes.

Place your oven rack in the center of the oven and preheat the oven to 400°F.

make the filling:In a large bowl, whisk together the eggs and sugar. Add the remaining ingredients and whisk until smooth.

Remove the pie crust from the refrigerator and pour the filling into the chilled pie crust.

bake the pie:Bake the pie at 400°F for 10 minutes, then reduce the temperature to 350°F and bake for another 40 minutes. The filling will puff up in the center and jiggle slightly if you gently shake the pie, but a toothpick inserted in the center of the pie should come out clean. Let cool completely.