Tangy, custard-like buttermilk pie with a hint of vanilla is a simple, old-fashioned Southern family dessert. Creamy and delicate, this classic pie is a testament to making something extraordinary from humble ingredients.
Preheat oven to 350°F and position rack in the center. Place the unbaked pie crust into a 9-inch pie pan.
In a large mixing bowl, beat the softened butter with sugar on medium speed until light and creamy—about 2 minutes.
Add eggs one at a time, beating well after each addition. Stir in the flour until no lumps remain.
Whisk in buttermilk, vanilla extract, lemon zest (if using), and salt. Mix until smooth and well combined.
Pour the custard filling into the prepared pie crust. Sprinkle nutmeg evenly across the top.
Bake for 45–55 minutes, rotating halfway, until the center is just set and the top is golden. If edges brown too quickly, tent crust with foil.
Cool the pie on a rack until room temperature. For best cutting, chill for at least 2 hours before slicing.