1In a large saucepan, combine sugar and flour. Gradually stir in buttermilk and water until smooth. Cook and stir over medium heat until thickened and bubbly, about 4 minutes. Reduce heat; cook and stir 2 minutes longer. Remove from the heat.
• Stir in a small amount of hot filling into egg yolks; return all to the pan, stirring constantly. Bring to a gentle boil; cook and stir 2 minutes longer. Remove from the heat; stir in lemon juice and butter until butter is melted. Keep warm.
• In a small bowl, beat the egg whites on medium speed until soft peaks form. Gradually beat in sugar, 1 tablespoon at a time, on high just until stiff peaks form and sugar is dissolved.
• Pour the hot filling into pastry shell. Spread meringue evenly over hot filling, sealing edges to crust. Bake at 350° for 15 minutes or until the meringue is golden brown. Cool on a wire rack for 1 hour; refrigerate for at least 5 hours before serving. Refrigerate leftovers. Yield: 6-8 servings.