Combine The Eggs, Egg Yolks and sugar in a mixing bowl and beat until smooth. Add the lemon juice and lemon zest and mix. Place the bowl over a pot of boiling water or in the top of a double boiler and stir vigorously with a wooden spoon until the mixture thickens. This mixture will not curdle, so don't worry about overcooking it a little. Remove the bowl from the boiling water and stir in the butter until melted. Refrigerated, this will keep for up to 3 months.
To Make A Lemon Custard Pie: Preheat oven to 375F. Fill a 9-inch pie shell and bake for 15 minutes.
