While crust is baking make the lemon curd layer by whisking 4 eggs and ¾ cup of granulated sugar together. Mix only until combined. Do not overmix or you will end up with a lot of air bubbles. (Some bubbles are normal).
Add in the zest from two lemons and ⅓ cup of all purpose flour and mix just until combined.
Then pour in ¾ cups of lemon juice and mix just until combined.
Once the cookie crust has baked for 18-20 minutes, pour lemon mix over it and bake for an additional 20-25 minutes, just until the lemon layer has set and does not jiggle when lightly shaken.
Let cool completely on the counter, and then chill in the fridge for a few hours before cutting and serving them so that the lemon layer can completely set. (The bars do taste better at room temperature, so after cutting them let them sit out of the fridge for a little while before eating for the best taste!)
Once chilled, cut into 16 even squares.
Sprinkle a little powdered sugar on top for looks if desired and enjoy!