Pre-heat the oven to a temperature of 400°F.
In a large bowl, add the half cup butter and the sugar together and beat the mixture to the point it gets light and soft.
Add eggs and flour to the mixture and beat until everything is mixed. Then add the 1 teaspoon vanilla to the combo and beat repeatedly.
In a separate bowl, pour the buttermilk and add the dry mixture from the large bowl to it in small quantities. Add some part of the mixture and stir it in buttermilk until it dissolves. Repeat the act until the dry mixture is finished.
Pour the dissolved quantity over the unbaked pie crust gently and make sure the mixture is levelled up at the top and the sides. A levelled mixture on all sides will give the pie a good look after it is baked.
Put the deep dish pie crust into the oven and heat for a good 10 minutes. Then reduce the temperature to 350°F and bake for at least 1 hour until the pie turns golden brown. To avoid overbrowning of the pie, aluminium foil can be placed over the top of the pie in the last 30 minutes of baking.
To check whether the pie is ready or not, insert a knife or a toothpick in the centre and if it comes out clean, the dish is ready to eat.
The Buttermilk pie is generally liked when it is warm, not too hot or not too cold. But some people like it when it is refrigerated for 30 minutes.