Buttermilk-Lemon Chess Pie

Mix flour, salt, and sugar in a food processor. Add butter; pulse until pea-size pieces of butter form. Add 1/2 cup buttermilk; pulse until moist clumps form, adding more buttermilk by tablespoonfuls if too dry. Form into a ball; flatten into a disk. Wrap in plastic and chill for 1 hour. Preheat oven to 350 °F. Roll out dough on a lightly floured surface to a 14" round. Transfer to pie pan; gently press onto bottom and up sides of pan. Trim dough, leaving a 1" overhang; tuck overhang under. Crimp edges decoratively. Line with parchment paper or foil; fill with pie weights or dried beans. Bake crust until edges begin to brown, 30-35 minutes. Remove paper and weights; bake until golden brown, 25-30 minutes longer. Let cool completely.