Preheat oven to 350°F (175°C). Place pie crust in a 9-inch pie dish and set on a baking sheet.
In a large bowl, cream the softened butter and sugar until light and fluffy.
Add eggs one at a time, whisking after each until well blended.
Stir in flour and pinch of salt until smooth.
Add buttermilk, lemon juice, and vanilla. Whisk until fully combined.
Pour filling into the prepared pie crust.
Bake for 45–50 minutes until edges are set and center slightly jiggles.
Remove from oven and let cool completely at room temperature.
Chill for one hour before slicing for best texture.