Preheat the oven to 350F degrees. Line a 9x13 inch baking pan with parchment paper or foil sprayed with cooking spray. Set aside.
In a medium bowl sift together 2 1/2 cups all-purpose flour, 2/3 cups powdered sugar and 1/2 teaspoon salt. Add 3/4 cup (1 1/2 sticks) unsalted butter, melted until combined. This is easiest with an electric hand mixer but you can do it by hand.
Add the dough into the lined pan and press into a flat thin layer with the bottom of a cup.
Bake for about 20 minutes, until a light golden color around the edges.
Lemon Filling
Place 3 cups granulated sugar in a food processor or mixer, and add in 3 Tablespoons lemon zest. Pulse or blend until the zest is fully incorporated, and sugar is a light-yellow color.
Add 1 cup all purpose flour to the sugar mixture and blend well.
Add 1 cup fresh lemon juice and 8 large eggs, room temperature and blend until completely combined.
Pour the filling over the crust and place in the oven. Bake for about 25-35 minutes, turning the pan after 15 minutes. Check for doneness by wiggling the pan. If it doesn’t jiggle in the middle, it’s done. Do not overbake. Remove from the oven and allow to cool for an hour before chilling in the fridge for at least two hours.
Cut bars into desired size (I cut them into 16 bars) and dust with 1/4 cup powdered sugar (or more to taste.) Pro tip: Use a clean, sharp knife, and dampen the blade with a wet paper towel before each slice.
Notes
Please refer to my FAQ’s (Frequently Asked Questions) and ingredient list above for other substitutions or for the answers to the most common questions.
Serving sizes can change depending on how big or small you cut the bars.