1 1/4 cups all-purpose flour, plus more for rolling out the dough
1/4 teaspoon fine salt
5 tablespoons unsalted butter, chilled and cut into small pieces
1/4 cup shortening, frozen and cut into small pieces
3 to 4 tablespoons ice water
1 teaspoon freshly squeezed lemon juice
For the filling:
2 cups granulated sugar
2 tablespoons all-purpose flour
1/2 teaspoon fine salt
1 cup buttermilk, at room temperature
4 large eggs, at room temperature
4 large egg yolks, at room temperature
2 teaspoons vanilla extract
8 tablespoons unsalted butter (1 stick), melted
2 teaspoons finely grated lemon zest (from about 1 medium lemon)