Prepare and roll out pastry.
Line a 9-inch pie plate.
Trim pastry to 1/2 inch beyond edge of pie plate.
Flute edge; prick pastry.
Bake at 450° for 10 to 12 minutes.
Cool.
For filling, in medium saucepan combine sugar, cornstarch, flour, and salt.
Gradually stir in water.
Cook and stir over medium-high heat till thickened and bubbly.
Reduce heat; cook and stir 2 minutes more.
Remove from heat.
Separate egg yolks from whites; set whites aside for meringue.
Beat egg yolks slightly.
Stir about 1 cup of the hot mixture into the beaten yolks.
Return mixture to saucepan.
Bring to boil; cook and stir 2 minutes more.
Remove from heat.
Stir in butter or margarine and lemon peel.
Gradually stir in lemon juice, mixing well.
Turn into pastry shell.
Make Meringue for Pie using the 3 reserved egg whites.
Spread over hot filling; seal to edge.
Bake at 350° till golden, 12 to 15 minutes.
Cool.
Cover; chill to store.