Line an 8 x 8 inch (or 9" square pan) with foil or parchment paper. Set aside.
Preheat oven to 350 degrees F.
In a large mixing bowl, cut together the cold butter, all-purpose flour, and powdered sugar. Mixture may be crumbly. Press into bottom of prepared baking dish.
Bake crust in oven for about 15 minutes.
While crust is baking, make the lemon filling. Combine granulated sugar, flour, baking powder, eggs, lemon juice, and lemon zest.
Remove crust from oven and immediately pour mixture over the baked crust. Return baking pan to oven for an additional 20 minutes, or until edges are golden brown.
Remove bars from oven. To make glaze, whisk together powdered sugar with lemon juice. Drizzle over warm bars. Cool completely then refrigerate for about 2 hours.
When chilled, remove from pan by lifting the foil (or parchment) and cut into squares. Sprinkle with powdered sugar and enjoy!
Video
Notes
Use real lemons for the lemon juice. Bottle lemon juice doesn't have the same fresh flavor!
Chill your lemon bars. For best results, lemon bars have an enhanced lemon flavor when chilled, plus it let's them firm up some so they are easier to cut.
Speaking of cutting, the filling in lemon bars can be a little finicky when cutting. If you want PERFECT lemon squares, pop the bars in the freezer for half an hour before slicing.
Help! My powdered sugar has absorbed into my lemon bars. No fear. This happens. First, wait until the bars have cooled and chilled before adding your powdered sugar. It's best to sprinkle generously right before serving. But, if it absorbs again, just add more powdered sugar, you can't go wrong!