01 -
Set oven to 175°C and prepare work surface.
02 -
In a medium saucepan, whisk together granulated sugar, cornstarch, and salt. Gradually stir in water and lemon juice until smooth.
03 -
Heat mixture over medium, stirring continuously until thickened and bubbling. Boil for 1 minute, then remove pan from heat.
04 -
In a separate bowl, whisk egg yolks. Gradually incorporate several tablespoons of the hot lemon mixture into the yolks, whisking to combine, then return to the saucepan.
05 -
Return the pan to medium heat. Cook, stirring constantly, for 2 minutes. Remove from heat and blend in lemon zest and unsalted butter until completely smooth.
06 -
Pour the hot lemon filling into the pre-baked pie crust, spreading evenly.
07 -
In a clean bowl, beat egg whites and cream of tartar until soft peaks form. Gradually add sugar while beating until the meringue holds stiff, glossy peaks.
08 -
Evenly distribute meringue over the hot filling, ensuring it seals to the pastry edge to prevent shrinking.
09 -
Bake for 15–20 minutes, or until meringue is golden brown.
10 -
Allow pie to cool at room temperature for 1 hour, then chill in the refrigerator for at least 3 hours before slicing.