Lemon Curd Tart

Tart Shell
1 Line a 9-inch (22 cm) tart ring or a fluted tart pan with removable bottom with shortcrust pastry dough. Fully blind bake the crust according to directions in the pastry recipe. Let the tart shell cool completely.
Lemon Curd Filling
4 In a large mixing bowl, whisk together half of the sugar (90 grams), whole eggs, and egg yolks until frothy. Whisk in a quarter of the sifted cornstarch at time, until completely dissolved. If it accidentally gets lumps, run the whole mixture through a metal sieve. 
3 Using a medium saucepan on medium heat, warm the remaining half the sugar (90 grams), lemon zest, and lemon juice until the sugar has dissolved. 
5 Slowly pour the warm lemon juice, into the egg mixture while whisking. Pour everything back into the saucepan. 
6 Continue on medium heat and continue to stir the mixture with a whisk until it has thickened and reads 178-180°F (80-82°C) on an intsant read thermometer.
7 Remove from heat and push the warm lemon curd through a fine mesh strainer with a spatula into a clean bowl.
8 Allow the lemon curd to cool at room temperature until it reaches 140℉ (60℃) on the thermometer. We don't want the butter to immediately melt when added. if it's too hot. 
9 Whisk in the butter cubes until dissolved and the mixture is smooth. Option to use a handheld immersion blender to mix.
Fill and Chill
11 Pour the lemon curd filling into the pre-baked tart shell. Use an offset spatula to level the top. 
12 Place the tart in the fridge for 3-5 hours to set. The filling will firm in the fridge making it easy to slice. 
Swiss Meringue
14 Place a medium saucepan filled with 1-inch of water on medium heat.
15 In the metal bowl of a stand mixer, combine the egg whites and granulated sugar. Immediately whisk by hand to create a foamy liquid.
16 Set the mixing bowl on top of the saucepan to create a double broiler.
17 Whisk the egg whites and sugar continuously until the temperature on an instant thermometer reads 160°F (72°C). Carefully dip your finger into the hot sugar and rub the mixture between your fingertips. If you don't feel any grains of sugar, the mixture is ready. (about 6-8 minutes)
18 Remove the mixing bowl from the heat and wipe the bottom of the bowl dry with a towel. Place the bowl on the mixing stand fitted with the whisk attachment and begin whipping on high speed.
19 Continue to whip until a thick, glossy and marshmallow like meringue with stiff peaks is formed. Stiff peaks means the meringue will hold its shape and not sing back over on itself. Lift the whisk from the bowl and if the meringue is thick and creates a "peak" or point without slumping it's good to go. The bowl should be cool or at least room temperature to the touch. (about 8-10 minutes)
Final Topping 
21 Once the lemon curd filling is set, you can decorate the tart before serving. Transfer the whipped meringue to a plastic piping bag with your favorite piping tip. Pipe dollups or swirls of meringue across the top of the tart. 
22 Carefully toast the meringue with a kitchen torch on a low setting. Keep the torch moving to prevent over browning the meringue.
23 Slice and serve.