Preheat oven to 325 degrees. Line a 13x9-inch pan with foil so that ends extend over the side to make a handle.
Process Nilla Wafers into fine crumbs, then add butter. Press into the bottom of the pan and bake at 325 for 10 minutes.
Separate 1 of the eggs and refrigerate yolk until ready to use.
In a mixing bowl, beat the cream cheese, ONLY 1 CUP OF THE SUGAR, flour, lemon zest, 2 tablespoons the lemon juice and vanilla. Add egg white and remaining 3 whole eggs, 1 at a time, mixing on low speed after each just until blended.
Spread mixture over crust and bake for about 40 minutes or until it appears set. It may still be a bit shiny or appear undercooked, but if you baked it for 40 minutes it should be done. Allow it to cool at room temperature for an hour, then transfer to a refrigerator and chill for 4 hours. After chilling, you can go ahead and make the topping or lift from the pan, wrap and freeze tightly until ready to use.
To make the topping, take your egg yolk out of the refrigerator and put it in a small bowl. Beat it lightly with a fork and keep it near the stove.
In a saucepan, mix the cornstarch and remaining 3/4 cup of sugar. Add the 1/2 cup water gradually and stir in the remaining lemon juice (a little over 3 1/2 tablespoons). Bring just to boil on medium heat, stirring constantly until clear and thickened. Stir about 2 tablespoon of the hot cornstarch mixture into the egg yolk, then add to saucepan; stir until blended. Cook 1 minute or until thick and smooth.
Spread the lemon glaze over cheesecake and chill for at least an hour. Using the foil as a handle, lift from pan and cut into squares or bars.