Preheat the oven to 350°F (175°C). In a mixing bowl, combine flour, butter, and sugar until crumbly. Add egg yolk and cold water, mix until dough forms. Roll out and place in pie dish.

In a saucepan, combine sugar, cornstarch, and salt. Gradually stir in water. Cook over medium heat until thickened. Remove from heat and stir in beaten egg yolks, lemon juice, and zest. Add butter and mix well.

In a clean bowl, beat egg whites and cream of tartar until soft peaks form. Gradually add sugar and continue beating until stiff peaks form.

Pour the lemon filling into the crust. Spread the meringue over the filling, sealing the edges. Bake for 10-15 minutes until meringue is golden. Cool before serving.