Preheat the Oven: Begin by preheating your oven to 350°F (175°C).
Make the Filling: In a large mixing bowl, whisk together the sugar, flour, and salt until thoroughly combined.
Add in the Eggs: Crack the eggs into the bowl and whisk until everything is well mixed, introducing air for a fluffier texture.
Incorporate Flavorings: Stir in the vanilla extract, buttermilk, fresh lemon juice, and lemon zest until you have a smooth mixture.
Prepare the Crust: Pour the filling mixture into the unbaked pie crust, spreading it evenly.
Bake: Place the pie in the preheated oven and bake for about 30-40 minutes, or until the filling is set and the top is lightly browned.
Cool and Serve: Once baked, allow it to cool at room temperature. Serve with a dollop of whipped cream or a slice of fresh fruit if desired!