The Ultimate Lemon Meringue Pie

1. FOR THE FILLING: Adjust oven rack to middle position and heat oven to 325 degrees. Bring water, sugar, cornstarch, and salt to simmer in large saucepan, whisking constantly. When mixture starts to turn translucent, whisk in egg yolks, two at a time. Whisk in lemon zest and juice and butter. Return mixture to brief simmer, then remove from heat. Lay sheet of plastic wrap directly on surface of filling to keep warm and prevent skin from forming.
2. FOR THE MERINGUE: Bring water and cornstarch to simmer in small saucepan and cook, whisking occasionally, until thickened and translucent, 1 to 2 minutes. Remove from heat and let cool slightly.
3. Using stand mixer fitted with whisk, whip egg whites, vanilla, and cream of tartar on medium-low speed until foamy, about 1 minute. Increase speed to medium-high and whip whites to soft, billowy mounds, about 1 minute. Gradually add sugar and whip until glossy, stiff peaks form, 2 to 3 minutes.
4. Meanwhile, remove plastic from filling and return to very low heat during last minute or so of beating meringue (to ensure filling is hot).
5. Pour warm filling into cooled prebaked pie crust. Using rubber spatula, immediately distribute meringue evenly around edge and then center of pie, attaching meringue to pie crust to prevent shrinking. Using back of spoon, create attractive swirls and peaks in meringue. Bake until meringue is light golden brown, about 20 minutes. Let pie cool on wire rack until filling has set, about 2 hours. Serve.

APPLYING A MERINGUE TOPPING
1. Start by placing dabs of meringue evenly around edge of pie. Once edge of pie is covered with meringue, fill in center of the pie with remaining meringue.
2. Using rubber spatula, anchor meringue to edge of crust or it may pull away and shrink in oven.