⅔cup(76g)powdered sugar, plus extra to sprinkle on bars
12tablespoons(170g)butter, 1 1/2 sticks, at cool room temperature, cut into 1-inch pieces
For the Filling (see note for thicker filling):
1 ⅓cups(283g)granulated sugar
2teaspoonsgrated lemon zest, from 2 large lemons
⅔cupfreshly squeezed lemon juice, from 3 to 4 large lemons
Pinchof salt, about 1/8 teaspoon
Place an oven rack in the middle position and preheat the oven to 350 degrees F. Line a 9X13-inch baking pan with foil or parchment paper and lightly grease the foil/parchment (optional: it helps with removing the bars after baking, but you can instead grease the pan with nonstick cooking spray).
Whisk together the flour, powdered sugar, cornstarch, and salt (this can be done in a food processor or in a large bowl by hand). Add the pieces of butter and cut the butter into the dry ingredients using a pastry blender, two knives or your fingers (taking care not to melt the butter too much - you might try freezing the butter and grating it into the dry ingredients on the large holes of a box grater) or process in the food processor for 8 to 10 seconds and then as needed until the mixture resembles coarse meal.
Sprinkle the mixture into the prepared pan and press into an even layer on the bottom. Refrigerate for 15-30 minutes. Bake until very lightly golden brown on the edges, about 15-20 minutes.
For the filling, whisk together the eggs, sugar, salt, and flour in a medium bowl and then stir in the lemon zest, juice and milk to combine.
Pour the filling onto the warm crust; reduce the oven temperature to 325 degreesand bake for about 18-20 minutes until the filling feels slightly firm to the touch. Cool the bars to room temperature, sprinkle with additional powdered sugar and cut into bars.
Recipe Tweaks: as with any recipe, over the years, I'll find I've tweaked it a bit. This recipe has been on my site for over five years and in that time, I've found that I like the crust with a bit more butter (makes it less crumbly), so I use a full cup (increased from 1 1/2 sticks). The crust mixing method also works great if you just want to soften the butter and mix everything together with an electric hand or stand mixer and then press into the pan.Filling: for thicker filling, use 1/2 cup milk, pinch salt, 5-6 tablespoons flour, 1 tablespoon lemon zest, 1 cup fresh lemon juice, 6 eggs and 2 cups sugar.