In the bowl of a stand mixer, add Butter (1/2 cup) and Granulated Sugar (1/4 cup). Mix until combined. Slowly add in All-Purpose Flour (1 cup) and Salt (1/4 teaspoon), continuing to mix as you do so, until the mixture comes together as a dough.
Transfer the dough to a 9-inch square pan lined with aluminum foil. Press it down into an even layer.
Bake at 350 degrees F (180 degrees C) for 15-20 minutes.
In a mixing bowl, add Egg (3), Granulated Sugar (1 cup), Lemon (1/2 cup), Lemon (1), Baking Powder (1/2 teaspoon), and All-Purpose Flour (1/2 cup). Mix until combined.
Pour lemon filling into the cooled crust. Bake for 25 minutes.
Place bars into the fridge for 2-3 hours.
Slice into squares. Dust with Powdered Confectioners Sugar (to taste). Serve and enjoy!