Keep the diced butter and ice water in the refrigerator until ready to use. Using a stand mixer bowl, weigh out the flour and add the salt. Mix using the paddle attachment on the lowest speed (stir) for about 10-seconds.
Add chilled diced butter to the bowl. On the lowest speed, turn the mixer on and off quickly for a few seconds. This helps to prevent the flour from spilling over. Continue to mix on low speed until the flour and butter has a mealy texture like wet sand and pea-sized pieces evenly throughout, about 60 to 70-seconds. Do not overmix. The dough should not bind together before the water is added. Alternatively, use a dough/pastry blender or your fingers to break the butter into the dough.
Gradually add 1 tablespoon of ice-cold water to the bowl. After each addition, turn the mixer on for 2 to 3-seconds. Only add enough water until the dough looks lumpy and hydrated, but not wet or sticky. It should begin to clump together with small crumbles on the bottom of the bowl. All of the water may not be needed, about 5 to 7 tablespoons is typical. When the dough is pinched together, it should compress and hold, not be dry or crumbly. Do not over mix. The dough will be pressed together before resting.
Press the dough into a 1” thick round disc, wrap it in plastic, and place it in a resealable bag. Store in the refrigerator to rest for at least 4-hours, overnight or up to 2 days. Once removed from the refrigerator, allow the crust to sit at room temperature for about 5 to 10-minutes. This will make it easier to roll. If it’s still too hard, let it sit at room temperature until more pliable.
Dust the counter and dough with flour. When rolling out, make sure to rotate and dust with flour underneath and on the top. This will prevent sticking and make it easier to transfer. Roll into a 14-inch circle, slightly less than ¼-inch thick.
Place the rolled out dough into a 9-inch pie dish and gently press against the sides and bottom. With a paring knife, trim the excess leaving a ½-inch overhang. Tuck the excess underneath the bottom crust edges. Crimp by pinching the pointer and thumb fingers.
Place the crust in the freezer for 20 minutes. Place the oven rack in the center position. Preheat to 375°F (190°C). Place the pie crust on a sheet pan.
Place a piece of parchment paper inside the pie dish and add the pie weights to cover just the bottom and sides of the crust, do not overfill. Bake for 20 minutes. Remove from the oven, and allow the weight to sit in the crust for a few minutes to press down any puffed areas. Carefully lift the parchment paper filled with weights out of the pie dish and set aside, it will not be used again.
Bake for 15 minutes, check to see if the bottom and sides have shrunken slightly. Use a spoon to gently press the bottom down and sides up, don’t force it too much. Bake the crust until golden brown and dry, about 10 to 15 minutes. Transfer to a cooling rack until completely cooled, 30 to 40 minutes.
In a small bowl, whisk together ½ cup sugar and cornstarch. In a medium bowl, whisk together ½ cup plus 1 ½ teaspoon water and egg yolks. Whisk in the cornstarch mixture. Set aside.
In a medium saucepan, add 1 ½ cup water, ½ cup sugar, lemon zest, lemon juice, and salt. Stir together and simmer over medium-high heat. Once the mixture reaches 190 to 200ºF (87 to 93ºC), about 3 minutes, turn off the heat.
Place the bowl with the egg mixture nestled in between a kitchen towel. Temper the eggs by slowly ladleing in ¼ cup (60 ml) of the hot lemon mixture into the egg mixture, whisking continuously. Continue this process until a total of 1 ¼ cups of the lemon mixture is added.
Whisk in the tempered egg mixture into the remaining lemon mixture in the pot. Turn the heat to medium-high, continuously whisk until the mixture thickens. Be careful not to scramble the eggs, about 3 to 5 minutes. Turn off the heat and whisk in the butter.
Immediately strain the lemon filling through a fine-mesh strainer into a clean bowl using a spatula to press. Cool the filling until its warm but spreadable, about 100ºF (37ºC). Evenly spread the lemon filling into the fully baked and cooled pie shell. Cover the surface with plastic wrap, directly on top of the filling to prevent a film from forming. Chill in the refrigerator until the filling is set, about 6 hours or refrigerate overnight. Once set, make the meringue topping.
Make sure the bowl of a stand mixer and the whisk attachment are clean. Any grease or fat will not allow the egg whites to whip up. Add the egg whites, vanilla extract, and pinch of salt. Set aside until sugar syrup is ready.
In a clean medium saucepan, add the sugar and water. Use a wooden spoon to carefully mix together. Make sure the sides of the pot are free of any sugar. If any sugar is left on the sides it can become hard and crystallize, causing the rest of the sugar to do the same. Use a pastry brush dipped in water and rub along the sides of the pot or pan where there is exposed sugar.
Heat saucepan over medium-high heat. Use a candy thermometer and place it in the pot, or check with an instant-read thermometer. Cook sugar to 240°F (115°C) which is considered the "soft ball" stage of cooked sugar.
Immediately start the mixer on speed 6. Whip the whites until foamy and bubbly but no peaks form, about 1 minute. Do not turn the mixer off, increase the speed to 8. Immediately add the hot sugar in a steady and single stream. This should take about 30 to 45 seconds.
After all the hot sugar has been added increase the speed to 10. Whip until the meringue becomes thick and shiny, can hold its peak, but not too stiff and/or foamy. The bottom of the mixing bowl should feel lukewarm but cold, about 3 to 4 minutes.
Take the filled pie shell out of the refrigerator. Remove the whipped whites from the mixer. Using a rubber spatula put the meringue on the pie. Using an off-set spatula gently spread the meringue around, giving a rustic appearance.
Toast the meringue with a hand-held cooking torch, until parts of the surface are golden brown.
No yolks in the whites: When separating the eggs into yolks and whites, make sure that reserved whites have no yolks in them. Otherwise, it will be harder to make a light and airy foam.
Storing: Refrigerate the pie for up to 1 day. Place a piece of plastic wrap against the cut or exposed pie.
Baking the meringue: Place the pie on a baking sheet and bake at 400ºF (204ºC), until some of the surface turns golden brown, about 4 to 6 minutes. Cool to room temperature on a wire rack, serve immediately.
Serving: It’s best to serve the pie right away for the best texture. If not eating right away, store in the refrigerator, but enjoy the same day. To slice, run a knife under warm water, then dry it off, and then make a single cut. Repeat the process for making every cut. This makes for clean slices.