In small bowl, combine graham cracker crumbs, margarine and 1 tablespoon sugar; mix well. Press onto bottom and up sides of 9-inch pie plate coated with nonstick cooking spray. Bake at 350° 8 to 10 minutes or until golden brown. Cool on wire rack.
In heavy saucepan, combine cornstarch, salt and 3/4 cup sugar. Gradually stir in water and buttermilk until smooth. Bring to boil; cook and stir 2 minutes or until thickened. Remove from heat. Stir small amount of hot filling into egg substitute. Pour heated egg substitute mixture into hot filling, stirring constantly. Bring to low boil, cook and stir additional 2 minutes. Remove from heat. Stir in lemon juice and lemon peel. Pour into crust. Cover and refrigerate at least 4 hours. Just before serving, spread whipped topping over filling.