Combine flour, powdered sugar, salt, butter, and lemon zest to a large mixing bowl. You can either use an electric hand mixer, food processor, or a pastry blender.
Spray a 13 x 9-inch glass baking dish with non-stick spray.
Press the cookie base into the baking dish using your fingers.
Bake the lemon cookie base for about 20 minutes.
While the crust is baking make the lemon filling. Beat the eggs in the same bowl used for the cookie base if possible.
Add the lemon juice, lemon zest, sugar, flour, and salt to the beaten eggs. Mixt well.
After the crust has baked for 20 minutes, remove it from the oven and slowly and carefully pour in the lemon filling.
Return the lemon cookies to the oven and continue to bake for 20 - 25 minutes. The Lemon Cookie Bars are done when the center of the filling has set, and the top of the bars are just starting to turn a golden brown color.
Remove from the oven and cool the cookie bars on a wire rack.