The secret to the towering meringue is that it uses eight egg whites, more than twice the amount in typical meringue pies.
Mix flour, sugar, salt in bowl. Using pastry blender, cut in margarine until coarse crumbs form. Gradually add water, tossing with fork, until pastry comes together.
Roll pastry out on floured surface to 13-inch circle. Roll pastry up on rolling pin; unroll into 9-inch pie plate. Fit into plate; don't stretch. Roll edge under for stand-up edge; flute. Chill 30 minutes.
Heat oven to 425 degrees F. Prick crust all over with fork. Line with foil; fill with dried beans or rice.
Bake in 425 degree F oven 15 minutes. Remove foil and beans. Bake 8 to 10 minutes, until edge is golden. Cool.
Grate 2 tablespoons rind, squeeze 3/4 cup juice from lemons. Mix sugar, cornstarch, salt in saucepan. Stir in water, lemon juice. Cook over medium heat, stirring, until thickened and bubbly, 15 to 20 minutes. Cook another 2 to 3 minutes, stirring. Remove from heat.
With fork, beat yolks in bowl; stir in 1/2 cup hot lemon mixture. Stir yolk mixture into lemon mixture in pan. Cook over low, stirring, 1 minute (don't overcook or eggs will set). Off heat, add butter, rind. Pour in crust.
Place oven rack in lower third of oven. Heat oven to 325 degrees F.
Beat 8 egg whites and cream of tartar in large bowl until foamy. On high speed, slowly beat in 3/4 cup sugar, a tablespoon at a time, until stiff peaks form. Spoon meringue over filling, spreading to edge of crust to seal to prevent shrinkage. Swirl in peaks.
Bake pie in lower third of 325 degree F oven 30 minutes (instant-read thermometer inserted in meringue registers 140 degrees F). Bake 3 minutes longer. Cool on rack at room temperature up to 2 hours. Refrigerate at least 1 hour. Pie may be refrigerated longer, but meringue will not cut as well. Makes 8 servings.