A good lemon meringue pie is the stuff dreams are made of. Just one look at this swoon-worthy dessert, with its tall, glossy peaks and tart lemon custard and you’ll want— no, need— an extra large slice. Maybe you should make two...
In a food processor (or see notes for the Hand-Mixing pie dough method), combine flour, sugar, and salt. Pulse until combined.
Scatter shortening pieces over the top and process until the mixture resembles coarse cornmeal, about 10 seconds. Scatter butter pieces and pulse until the mixture resembles coarse crumbs, about 10 seconds. Transfer to medium bowl.
Sprinkle 4 tablespoons ice water over mixture. Using a stiff rubber spatula, stir and press dough together until it sticks together. Add more ice water, 1 tablespoon at a time, if necessary until dough comes together.
Turn dough out onto a sheet of plastic wrap and flatten into a 4-inch disk. Wrap tightly in plastic wrap and refrigerate for 1 hour. Before rolling out dough, let soften at room temperature for 10 minutes.
Roll dough into a 12-inch circle and fit into a 9-inch pie plate. Trim, fold, and crimp the edge of the dough. Wrap the dough-lined plate and place in the freezer until dough is fully chilled and firm, about 30 minutes.
Adjust an oven rack to the middle position of the oven and preheat to 375 degrees. Line the chilled pie shell with a double-layer of aluminum foil and fill with pie weights.
Bake until the pie dough is lightly browned and dry, about 25 to 30 minutes. Remove foil and weights and bake until the crust is a deep golden brown, about 10 to 12 minutes longer. Transfer to a wire rack and cool to room temperature.
In a large saucepan over medium heat, whisking constantly, bring water, sugar, cornstarch, and salt to a simmer. When the mixture starts to turn translucent, whisk in egg yolks, 2 at a time.
Whisk in lemon zest, lemon juice, and butter. Return to simmer and immediately remove pan from heat.
Pour filling into baked and cooled pie crust. Cover with plastic wrap (pressed down directly on surface of filling) and refrigerate until cold, about 2 hours.
Adjust an oven rack to the middle position and preheat to 400 degrees.
In a small saucepan over medium-high heat, bring sugar and water to boil and cook until mixture is slightly thickened and syrupy, about 3 to 4 minutes (235 degrees on a candy thermometer). Remove from heat and cover to keep warm.
In a standing mixer fit with the whisk, or in a large bowl with an electric mixer, whip egg whites, cream of tartar, and salt together on medium-low speed until foamy, about 1 minute.
Increase mixer speed to medium-high and whip until whites are shiny and soft peaks form, about 1 to 3 minutes.
Reduce mixer speed to medium and slowly drizzle warm syrup (avoid the whisk attachment and sides of bowl). Add vanilla, increase speed to medium-high, and whip until mixture has cooled slightly and is very thick and shiny, about 3 to 6 minutes.
Dollop the meringue evenly over the top of the chilled lemon filling and spread, making sure it adheres to the crust. Use the back of a spoon to create attractive swirls and peaks.
Bake until meringue is golden brown, about 6 minutes. Transfer to a wire rack and cool until filling has set, about 2 hours. The pie can be wrapped and stored at room temperature for 1 day.
To serve, cut into wedges using a thin, sharp knife dipped into hot water between cuts. Or, hold at room temperature for up to 4 hours. The pie is best eaten the day it is baked, but it can be stored at room temperature for 1 day.