Lemon Meringue Pie

prepared pie crust baked in a 9” pie plate
1 ¼ cups sugar
1/3 cup cornstarch
pinch salt
1 1/3 cup water
2/3 cup fresh-squeezed lemon juice
4 tsp finely grated lemon zest
4 large eggs yolks (reserve whites)
3 tbs butter, cut into small pieces
In a medium pot, whisk together sugar, cornstarch and salt. Thoroughly whisk in water and lemon juice, then the zest and egg yolks. Place over medium heat and, whisking constantly, bring to a simmer. Add butter and continue to cook for 1 minute. Scrape into prepared pie crust and cover with plastic wrap.
For the meringue: Squeeze 1 tsp lemon juice into a large glass or metal bowl, then add 4 egg whites (2/3 cup). Using an electric mixer fitted with the whisk attachment, beat whites until soft peaks form. Continue beating, while very gradually adding ½ cup sugar, until stiff peaks form.
Remove plastic wrap and spread the meringue over the top, sealing it to the edges of the crust. Back at 325F for 15-20 minutes. Cool completely on a wire rack. Refrigerate.