Unfold and stack piecrusts on a lightly floured surface. Roll into 1 (12-inch) circle. Fit piecrust into a 9-inch pieplate (about 1 inch deep); fold edges under, and crimp. Prick bottom and sides of piecrust with a fork. Freeze 10 minutes.
Line piecrust with parchment paper; fill with pie weights or dried beans.
Bake at 425° for 10 minutes. Remove weights and parchment paper; bake 12 to 15 more minutes or until crust is lightly browned. (Shield edges with aluminum foil if they brown too quickly.)
Prepare Lemon Meringue Pie Filling; pour into piecrust. Cover with plastic wrap, placing directly on filling. (Proceed immediately with next step to ensure that the meringue is spread over the pie filling while it is still warm.)
Beat egg whites and vanilla extract at high speed with an electric mixer until foamy. Add sugar, 1 tablespoon at a time, and beat 2 to 4 minutes or until stiff peaks form and sugar dissolves.
Remove plastic wrap from pie, and spread meringue evenly over warm Lemon Meringue Pie Filling, sealing edges.
Bake at 325° for 20 to 25 minutes or until golden brown. Cool pie completely on a wire rack. Store leftovers in the refrigerator.