Put the flour, salt and sugar in the bowl of a food processor
and pulse a few times to combine. Sprinkle half of the butter cubes over the top of the flour and process for 10 seconds. Sprinkle the remaining half of the butter over the mixture and pulse
until the mixture resembles coarse cornmeal
, with some butter bits no bigger than peas
. With the motor running, add the buttermilk
through the feed tube and process until the dough just begins to come together. Transfer to a flat surface and lightly knead
until the dough comes together. Form into 2 flat disks, wrap in plastic wrap
and refrigerate for at least 1 hour. (You will need only 1 for the pie; the remaining dough can be frozen for up to 1 month.)
Lightly spray a 9-inch tart pan with a removable bottom with nonstick spray. Roll the dough
on a lightly floured surface into a 12-inch round that is 1/8-inch thick and fit it into the tart pan
. Roll rolling pin over tops of pan to trim dough flush with rims and lightly prick bottoms and sides all over with a fork. Place in the freezer for 30 minutes.
Preheat the oven to 375 degrees F. Place the pan on a baking sheet. Spray the shiny side of a 12 piece of aluminum foil and line the shell shiny-side down with the foil and fill with pie weights
. Bake on the middle rack in the oven until the crust
sets and turns a pale golden brown, about 20 to 25 minutes. Remove the foil and pie weights and continue baking until golden brown and baked through, about 15 minutes longer. Transfer the tart pan to a baking rack and let cool completely, about 1 hour.