Set your oven to 350°F (175°C). Let it heat up completely while you prepare the filling. A hot oven ensures the custard sets properly. Place your rack in the center position for even baking.

In a large bowl, beat the eggs and sugar together. Use a whisk or a hand mixer on medium speed. Mix until the mixture looks light and fluffy. This step creates a smooth base for your pie.

Pour the melted butter and buttermilk into the bowl. Make sure the butter is not hot, or it might cook the eggs. Whisk gently until the liquids are fully combined. The smell will already be wonderful.

Add the flour and the pinch of salt to the wet mixture. Whisk carefully so no lumps remain in the batter. The flour helps the pie set up into a firm but creamy custard texture.

Stir in the vanilla extract and the fresh lemon juice. These ingredients give the pie its signature Southern aroma. Use a spatula to scrape the sides of the bowl. Make sure every drop is incorporated well.

Place your unbaked pie crust on a sturdy baking sheet. Carefully pour the buttermilk mixture into the shell. Do not overfill it, as it might bubble over. Sprinkle a little nutmeg on top if you like.

Slide the baking sheet into the oven. Bake for 50 to 60 minutes. The center should have a slight jiggle like Jell-O. The top should be a beautiful, light golden brown color.

Remove the pie from the oven carefully. Place it on a wire rack to cool completely. This part is hard, but you must wait. The pie needs time to firm up before you slice it.