2/3 cup plus 3 tablespoons nonfat buttermilk, divided
3/4 cup sugar
1/4 cup plus 2 tablespoons cornstarch
1/8 teaspoon salt
1 cup water
1/2 cup frozen egg substitute, thawed
2 teaspoons grated lemon rind
1/2 cup fresh lemon juice
5 egg whites
1/2 teaspoon cream of tartar
1/2 teaspoon vanilla extract
1/4 cup sugar
How to Make It
Combine first 3 ingredients in a bowl; cut in margarine with a pastry blender until mixture resembles coarse meal and is pale yellow (about 3 1/2 minutes). Sprinkle 3 tablespoons buttermilk over surface; toss with a fork until dry ingredients are moistened and mixture is crumbly.
Gently press mixture into a 4-inch circle on heavy-duty plastic wrap; cover with additional heavy-duty plastic wrap, and chill 15 minutes. Roll dough, still covered, to a 10 1/2-inch circle. Remove plastic wrap, and fit dough into a 9-inch pieplate. Roll edges under, and flute. Prick bottom of pastry with a fork. Bake at 450° for 10 minutes or until lightly browned; cool completely on a wire rack.
Combine 3/4 cup sugar, cornstarch, and 1/8 teaspoon salt in a saucepan; gradually stir in water and remaining 2/3 cup buttermilk. Cook over medium heat, stirring constantly, until mixture comes to a boil. Cook, stirring constantly, 1 minute. Remove from heat.
Gradually stir about one-fourth of hot mixture into egg substitute; add to remaining hot mixture, stirring constantly. Cook over medium heat, stirring constantly, 2 minutes or until thickened. Remove from heat; stir in lemon rind and lemon juice. Spoon into pastry shell.
Beat egg whites, cream of tartar, and vanilla at high speed of an electric mixer until foamy. Gradually add 1/4 cup sugar, 1 tablespoon at a time, beating until stiff peaks form and sugar dissolves (2 to 4 minutes). Spread meringue mixture over hot filling, sealing to edge of pastry. Bake at 325° for 25 minutes or until golden. Cool completely on a wire rack.