This easy Old Fashioned Lemon Squares recipe starts with a delicious buttery shortbread crust, filled with a creamy, gooey oh-so lemony center and finished with a thick layer of powdered sugar lemon glaze. The essential Lemon Bar recipe!
Preheat oven to 350F degrees and line a 9x13 inch pan with parchment paper or foil.
Shortbread Crust | Blend together the softened butter, vanilla, sugar and flour in a mixing bowl or stand mixer on low until smooth and combined.
Prep & Bake the Crust | Press the shortbread batter into the bottom of a parchment lined or well sprayed 9x13 inch baking pan <== my favorite pan company! Using a sheet of parchment or wax paper, press the batter evenly into the bottom of the pan. Bake at 350F degrees for 15-20 minutes, just until firm and starting to turn golden.
Make the Fresh Lemon Filling
While the crust is in the oven; in a large mixing bowl, whisk together the sugar and flour.
Whisk in eggs into mixture, whisking well until frothy and sugar has dissolved, (cane sugar will take a little longer) then slowly whisk in lemon juice and zest from one-two lemons. (more is better in my opinion, but I like it tart!)
Pour lemon filling over the hot, baked shortbread crust (or almond flour shortbread crust), returning to the oven for an additional 15-20 minutes. Give the filling a final whisk just before you pour it over the hot crust.
Bake until the filling feels firm when lightly touched. Lemon squares will firm up and set as they cool. Remove from oven and cool on a wire rack.
Prepare Lemon Powdered Sugar Glaze
Mix powdered sugar, lemon zest into medium mixing bowl, whisk to combine, slowly add lemon juice, whisking until glaze is desired consistency.
Once the lemon squares have cooled on a wire rack for about 20 minutes, then pour and smooth over warm (not hot) lemon shortbread cookie bars.
Cool completely, then cover and refrigerate.
*If desired, omit the lemon glaze and dust generously with powdered sugar instead. Be sure to wait until lemon bars are completely cooled.
Notes
GLUTEN FREE LEMON BARS
Swap the Flour | For the shortbread crust, swap out the regular AP flour for a good Gluten Free AP Flour (my favorite), or try using GF Almond Flour for a delicious Almond Flour Shortbread crust.
Replace the AP flour in the lemon filling for equal amounts of GF AP Flour.
Baking Tips
COOL COMPLETELY | Allow the lemon squares to cool completely, it is actually much easier if you can refrigerate them for a few hours or overnight before you slice them.
REMOVE FROM PAN | Using the parchment paper as a sling, remove cooled old fashioned lemon squares from the pan onto a cutting board.
KNIFE | Run a long, sharp knife under warm or hot water, I keep a glass nearby with a paper towel to dry off between slices.
CUT | Using the warm knife, cut into desired square sizes, wiping off in between slicing.
SERVING | Lemon Squares will come to room temperature pretty quickly, it's fine to serve them that way, but the glaze will weep a bit, which isn't bad. For individual serving ideas, place in a cupcake wrapper and serve unstacked on a tray.
LEMONS | See post for how to get the most juice and zest from your lemons.