Preheat oven to 450°.
Bake 1 piecrust in a 9-inch pie-plate according to package directions. Set aside. Reduce oven temperature to 350°.
Combine gelatin and boiling water in a saucepan, stirring until gelatin dissolves. Stir in cold water; let stand 10 minutes.
Add egg yolks, cornstarch, and lemon juice; stir. Place over medium heat; cook, stirring constantly, until mixture comes to a boil. Boil 1 minute. Remove from heat; stir in sweetener. Pour into crust.
Beat egg whites and cream of tartar with a mixer at high speed until foamy. Add fructose; beat until stiff peaks form. Spoon meringue smoothly over filling. Bake at 350° on lower rack in oven for 12 minutes. Cool on a wire rack; chill.