To prepare the pie crust, preheat oven to 350°F (175°C).
Roll the pie crust into 10-inch circle on floured surface.
Transfer it to 9-inch pie pan, fold the edges and pierce holes with a fork.
Now we need to blind-bake the crust to prevent the crust to puff up. In order to do that, cover the crust with a foil and pour raw rice or bean on top (or pie weights).
Bake for 15 minutes. Then remove the foil with rice/beans and bake for another 15-20 minutes, or until golden brown.
To make the meringue, in a small bowl, whisk together sugar and cornstarch.
In a large mixing bowl with whisk attachment, beat egg whites until foamy.
Then slowly add sugar mixture one tablespoon at a time and continue to beat on medium high speed until hard peaks form. Set aside.
To make the lemon curd filling, in a medium saucepan, mix together water, lemon juice, sugar, cornstarch, flour, lemon zest and salt. Bring the mixture to a boil over medium heat, stirring constantly.
To temper egg yolks, add about half cup of lemon juice mixture into the egg yolks and stir vigorously. Return the egg mixture back to the saucepan. Continue cooking for 3-5 minutes, continuously stirring.
Throw in the butter.
While butter is melting in the filling, briefly whisk the egg whites for a minute.
To assemble the pie, transfer the hot filling into pre-baked pie crust and immediately spread the meringue over the filling making sure to seal the edges.
Bake the pie for 8-10 minutes, or until meringue is golden brown.
Cool completely on wire rack at room temperature, 1-2 hours, before serving.