For crust: In the work bowl of a food processor, pulse together flour, sugar, and salt. Add cold butter, pulsing until mixture is crumbly. Gradually add buttermilk, pulsing until a soft dough forms. Turn out dough onto a lightly floured surface, and shape into 2 disks. Wrap tightly in plastic wrap, and refrigerate until firm, about 30 minutes.
Position oven rack to lowest setting, and preheat oven to 425°.
For filling: Separate hulls from pulp of grapes. (See tip below.) Place grape hulls and ½ cup water in a medium saucepan. Place grape pulp in a separate medium saucepan. Bring both pans to a boil over medium-high heat. Cook for 15 minutes, stirring both frequently. Remove from heat. Stir sugar into hull mixture. Strain pulp mixture through a fine-mesh sieve, discarding solids. Add pulp juice to hull mixture.
Place hull mixture in the container of a blender, and pulse several times to break hulls into smaller pieces. Pour mixture into a large bowl. Stir in cornstarch, egg, zest, vanilla, and cinnamon.
On a lightly floured surface, roll half of dough into a 12-inch circle. Transfer to a 9-inch pie plate, pressing into bottom and up sides. Pour filling into prepared crust.
Roll remaining dough into a 12-inch circle, and cut dough into 1½-inch-wide strips. Arrange strips in a lattice design over filling. Brush dough with cream, and sprinkle with turbinado sugar. Place pie on a rimmed baking sheet.
Bake for 20 minutes. Reduce oven to 375°, and bake until crust is golden brown and filling is bubbly, about 30 minutes more. Let cool on a wire rack for at least 45 minutes before serving. Serve with ice cream, if desired.
Notes
Kitchen TIP To save time, use 1 package of refrigerated piecrusts instead of making a homemade crust.
Recipe by Taste of the South at https://www.tasteofthesouthmagazine.com/muscadine-pie/