In a pie tin or glass pie pan, mix together flour, salt and sugar. Mix together vegetable oil and milk. Pour onto dry and mix with fork until mixture forms a ball. With your hands, pat mixture into pan and up the sides, forming the crust.
Filling
Cut lemon into small chunks leaving rind on. Remove seeds. In a blender or food processor, blend together lemon chunks, eggs, butter, vanilla extract and sugar until mixture is smooth and creamy. Pour into unbaked pie crust.
Bake for about 40 minutes. If crust becomes too brown, cover gently with foil and finish baking.
Serve with a dollop of fresh whipped cream, if desired.