In a saucepan that a bowl can sit on top of or double broiler, pour about 2 inches of water and bring it to a simmer. (The bowl should be able to sit on top without touching the water)

In a bowl, add lemon juice, eggs, egg yolks, sugar, and salt. Place the bowl on the saucepan and whisk the curd continually until the mixture becomes very think, this will take about 10-12 minutes (or it is 180° F on a thermometer.)

Remove the bowl from the saucepan and cool until it reaches 140° F, stirring from time to time to release the heat.

While it is cooling, cut butter into 1-tablespoon cubes. When the curd is ready, whisk in the butter 1 tablespoon at a time, stirring until melted after each piece.

Once all the butter is added, the curd will be pale yellow and thick.

Pour into your baked pie pan and press a piece of plastic wrap on top to prevent the curd from forming a skin. Set in the fridge for 3-4 hours or overnight until set before topping with meringue.

Use a double boiler or create one using a bowl and pan. Fill the pan with 2” warm water and place a bowl over the pan so it can heat the egg whites with the steam, but it should not touch the bottom

Add egg whites, sugar, and cream of tartar to the bowl. Place the bowl over the warm water. The pan should not touch the bottom but be heated by the steam

On low, heat the egg white mixture stirring constantly until gently warmed and the sugar is dissolved. Be very careful at this stage to not let the egg whites cook. Scrape the sides of the pan, stir constantly, and remove when sugar dissolves

Once dissolved, whip the egg whites on high until stiff peaks form. The mixture will be very glossy and thick. When you place the whisk into the eggs and pull up, it should create a peak. Once it reaches this point, add in the vanilla and mix to evenly combine.

Add the meringue over the set, chilled pie. Toast with a blow torch or in an oven on the broil setting for ~1-3 minutes keeping a close eye so it does not burn.

Slice and serve. The pie should be kept in the fridge after topping.