Preheat oven to 350°F (175°C)
Beat butter and sugar in a bowl until light and fluffy
Mix in flour and salt gradually, stopping when the crust resembles coarse crumbs
Press the crust firmly into a 13×9-inch pan using a flat-bottomed cup
Freeze the crust for 15 minutes to firm it before baking
Bake the crust at 350°F (175°C) for 20 minutes until golden brown
Remove from oven and let cool slightly while preparing filling
Whisk egg yolks, lemon zest, and 3/4 cup fresh lemon juice until blended
Heat 1/3 cup melted butter and 1/3 cup warm sugar, then gradually pour into the egg mixture, stirring constantly
Incorporate 2 tbsp cornstarch into the mixture and whisk until smooth to create a custard-like texture (step estimated from context)
Strain the filling through a fine mesh sieve for a silky consistency
Pour the filling evenly over the cooled crust and bake at 325°F (162°C) for 15 minutes
Cool the bars completely, then refrigerate for 30 minutes to set them before glazing
Mix powdered sugar with cold lemon juice (1 tbsp) and pour over the filling while still cool
Return to the freezer for another 15 minutes before slicing into 24 bars