Melt butter over very low heat; stir in sugar and lemon rind and juice. Beat yolks and whole egg together and add to mixture when sugar is dissolved. When thickened, remove from heat. Don't allow to boil!
Remove crusts from bread and cut or tear gently into large crumbs and scatter over the bottom of pie shell. Make a stiff meringue of the egg whites sweetened with 6 tablespoons of sugar. While lemon mixture is still hot, spoon it over breadcrumbs and cover with meringue.
Seal meringue to edges of pie shell. Brown in a 350-degree oven. Cool and serve at room temperature.