Preheat oven to 350°F. Position a rack in the center of the oven.
Prepare your crust. For a blind-baked crust, roll the dough out into the pie plate, then poke holes along the sides and bottom with a fork. Line with parchment paper, fill with pie weights (evenly distributed), and pre-bake for 10 minutes. Optionally, brush the crust with an egg wash (1 egg whisked with a teaspoon of water). If using a frozen crust, follow the package instructions for pre-baking.
Cream the room-temperature butter and sugar in a stand mixer or with a hand mixer until light and fluffy, about 3 to 4 minutes, on medium speed.
Add the cornmeal and flour.
Add the room-temperature eggs one at a time, beating well and scraping down the sides after each addition.
Add the room-temperature buttermilk, vanilla, lemon juice, lemon zest (if using), and salt. Beat until smooth.
Pour the filling into the pre-baked crust and carefully transfer to the oven.
Bake for 50 to 60 minutes, until the edges are firm but the center is still slightly jiggly (not liquidy). Continue baking if it's still liquidy. Check after 15 to 20 minutes and tent with foil if it's browning too much.
Remove from the oven and let cool on a wire rack to room temperature, about 3 hours, before serving.