Make the pie crust; add flour and salt to the bowl of a food processor. Pulse a few times.
Add cubed cold butter and process until coarse crumbs form. Transfer the mixture into a medium-sized bowl and sprinkle water over the dough.
Use a rubber spatula to press the dough together. shape the dough into a disc and wrap with a plastic foil.
Refrigerate the dough for 30 minutes up to 1 hour.
Make the filling:
Prepare the filling: beat butter and sugar in a large bowl until fluffy.
Add eggs, one at a time, beating well after each addition.
Fold in the flour and salt. Stir until smooth.
Add buttermilk, lemon juice, and vanilla. Stir to combine. Do not overmix. Set the filling aside and preheat your oven to 350°F.
Assemble:
Shape the pie crust; roll the pie crust dough on a slightly floured surface about an inch larger than the pie plate. I used a 9-inch pie plate.
Place the rolled dough over the rolling pin and gently transfer it into the pie plate.
Gently press the pie crust around the edges of the pie plate so it fits nicely in the bottom and the sides. Trim the excess dough and shape the edges. You can just pinch them to get that nice rim.
Pour the prepared buttermilk filling into the prepared pie crust.
Baking time:
Bake the buttermilk pie for 50-55 minutes.
Serve:
Cool the pie completely on a cooling rack before slicing and serving.
Serve with some whipped cream.
Notes
There is no need to pre-bake the pie crust for this pie.