This is a traditional southern pie for which recipes abound. The truly authentic pie has few ingredients and is delicious but extremely sweet (which is why it is sometimes called sugar pie). I experimented with a number of recipes before pulling my favorite features of the pie together here. The optional ingredients help give depth and brightness to its essentially sugary nature. —Starmade
Optional ingedients (not part of traditional pie but delicious): 2-3 tbsp rum; 2-3 tbsp lemon juice, grated lemon rind; nutmeg to sprinkle on top
traditional type pie shell (I like the cooks illustrated recipe)
First, if you don't happen to be working with a frozen pie shell, which usually I'm not, make your pie shell and put it in fridge to chill. Cook's illusrated recipe is good and works well here https://food52.com/recipes/24966-cook-s-illustrated-foolproof-pie-crust. If it has chilled overnight, so much the better.
Preheat oven to 400 and make the filling. Stir together sugar, salt and flour. Add the eggs and buttermilk and beat together till combined. Add melted butter. Add vanilla and any optional ingredients you see fit.
Pour in pie shell and bake for 10 minutes at 400
Turn down to 350 and bake another 50-60 minutes or until pie crust is brown and filling is slightly puffed and no longer jiggly in center. (If crust looks too brown you can tent with foil in last 30 minutes.)
Cool 45 minutes to an hour before attempting to eat the pie. Good slightly warm, room temperature, or chilled.