In a large bowl, whisk the flour, sugar, and salt together.
1¼ cups all-purpose flour, 1 teaspoon granulated sugar, ½ teaspoon kosher salt
Add in the butter and shortening, and use a pastry cutter or two forks to combine the ingredients until the butter and shortening are pea-sized pieces or smaller.
¼ cup unsalted butter, ¼ cup vegetable shortening
Add in 2 tablespoons of the water and stir until combined. Add the remaining tablespoons, one at a time, until the dough is crumbly, but begins to come together.
¼ cup ice water
Use your hands to gently knead the dough a few times until it comes together.
Turn the dough out onto a piece of plastic wrap and form it into a disc. Wrap tightly and refrigerate for at least 1 hour.
Preheat the oven to 375°F.
On a floured work surface, roll the chilled pie crust into a 12-inch circle. Transfer it to the pie plate and trim off any excess. Fold the edge of the crust under and use your finger and thumb to shape the crust.
Poke holes all over the bottom and sides of the crust.
Line the crust with parchment paper and fill with pie weights. Bake for 10-12 minutes or until the edges of the pie begin to look dry.
Remove from the oven and cool for 10 minutes. Remove the pie weights and continue to cool as you prepare the filling.
Reduce the oven temperature to 350°F.
In a large bowl, whisk the sugar and melted butter until combined.
1½ cups granulated sugar, ½ cup unsalted butter
Add in the flour, eggs and yolk, and whisk until combined.
3 tablespoons all-purpose flour, 3 large eggs, 1 large egg yolk
Finally whisk in the buttermilk, lemon zest, lemon juice, vanilla extract, nutmeg and salt.
1 cup buttermilk, 1 teaspoon lemon zest, 1 tablespoon lemon juice, 1 teaspoon pure vanilla extract, Pinch ground nutmeg, Pinch kosher salt
Pour the filling into the crust and bake for 45-50 minutes or until the middle is set. If the pie is browning too quickly, cover it with foil and continue cooking.
Let the pie cool completely at room temperature before slicing and serving.