Cut one of the lemons into paper thin slices. Squeeze juice from the other lemons.Pour juice over lemon slices along with sugar in bowl. Marinate for at least 3 hours, stirring occasionally.
Beat eggs and salt until frothy. Stir in butter and lemons. Pour into prepared pie shell. Bake at 450 for 15 minutes then adjust temp to 350 for another 30 minutes. Let cool and serve with whipped topping,