1. Preheat oven to 350°F (175°C).
2. In a mixing bowl, combine flour and butter until crumbly. Add cold water gradually until dough forms. Press into pie dish and bake for 10-12 minutes. Let cool.
3. In a saucepan, combine sugar, cornstarch, and salt. Gradually stir in water. Cook over medium heat, stirring constantly, until mixture thickens and boils. Boil for 1 minute.
4. Remove from heat. Stir in butter, egg yolks, lemon juice, and lemon zest. Return to heat and cook for 2 minutes. Pour into baked pie crust.
5. For meringue, beat egg whites and cream of tartar until soft peaks form. Gradually add sugar, beating until stiff peaks form. Spread over hot filling, sealing edges to crust.
6. Bake for 10-12 minutes or until meringue is golden brown. Cool on a wire rack. Refrigerate before serving.