As a note, I only used a small amount of powdered sugar on the top. While I love the touch of powdered sugar, when eating treats topped with the stuff I somehow always manage to inhale or exhale at exactly the wrong moment and end up covering myself with sugar or choking on it. So, for the sake of keeping these low maintenance to eat I kept the sugar minimal. You could obviously adjust this to match your personal taste.
1 c butter, softened
2 c flour
1/2 c sugar
pinch of salt
3 c sugar
1/2 c + 2 T flour
1 1/4 c fresh lemon juice (approx 5-6 large lemons or 7-8 small lemons)
zest from 2 lemons
powdered sugar to top (optional)
Preheat oven to 350 degrees. Use pastry cutter or just your hands to blend together all crust ingredients in medium bowl. Press into greased 9x13 pan. Bake for 20 minutes. Set aside to cool slightly while preparing the filling.
Whisk filling ingredients together in medium bowl until well combined. Pour over crust. Bake for an additional 30 minutes. Allow to cool in pan.
Sprinkle with powdered sugar to taste while still slightly warm. Once cool, cut into squares and serve.