Preheat oven to 375F.

Crush vanilla wafers in a food processor using a rolling pin. Add the sugar, and melted butter, and blend well. Press into bottom and along sides of a Pyrex pie baking dish. Bake at 375 F for approximately 8 minutes or until the crust is lightly browned.

Reset the oven to 350 F.

Combine sweetened condensed milk with egg yolks, and blend well. Slowly pour in lemon juice stirring constantly. Add a tablespoon of lemon zest and taste for sufficient lemon juice. Add one or two drops of yellow food coloring and mix well. Sprinkle the remaining lemon zest on the bottom of the pie crust. Pour lemon mixture into the pie crust.

Prepare the Meringue:
In a perfectly clean bowl, using a hand held electric mixer, beat the egg whites. When the whites start to become foamy, and soft peaks begin to form, slowly add the sugar, then the cream of tartar. beat until fairly stiff peaks form, and the whites are glossy. Mound on top of filling, and create decorative swirls. Spread meringue to overlap edges of pie crust slightly (meringue shrinks during baking). Bake in a 350 F oven until slightly brown, approximately 12 to 15 minutes.

Refrigerate until set, approximately 1 1/2 hours.