1.  To prepare crust, combine flour, sugar, and salt in bowl of food processor and pulse once or twice to mix. Add cold cubed butter and pulse three or four times, until butter is in pea-size pieces. Drizzle water over the flour mixture and pulse a few times, just until dough comes together in a shaggy ball.

2.  Divide dough in two and wrap each half tightly in plastic wrap, using plastic wrap to help gather up any loose crumbles of dough. Press each ball into a disk, transfer to refrigerator, and refrigerate 30 minutes before rolling (if you refrigerate it longer, let the dough stand at room temperature for 10 minutes before rolling). The dough will keep, refrigerated, for up to 3 days or it can be tightly wrapped and frozen for up to 3 months. Thaw overnight in the refrigerator before using.

3.  On a lightly floured work surface with a lightly floured rolling pin, roll the dough into a thin, even circle about 12 inches in diameter, beginning in the center and working outward.

4.  Preheat the oven to 350F.

5.  To prepare filling, whisk together sugar, melted butter, eggs, flour, lemon juice, lemon zest, vanilla, salt, cinnamon, and nutmeg in large bowl. Whisk in buttermilk, then pour filling into unbaked pie crust and bake until pie is golden brown on top and the center jiggles slightly, 45-50 minutes.

6.  Transfer to wire rack and let cool completely before slicing.