I made these lemon bars from All Recipes, using a few minor adjustments as mentioned in the comments and they came out delicious. I used extra lemon juice (2/3 cup plus additional flour), added some zest, and baked it in a smaller tray. They're a really nice summer dessert and very simple and easy to make.
The crust and filling take about 10 minutes longer to bake in the smaller tray (9x13 inch)
Fresh lemons (I only needed 3)
I didn't add powdered sugar to the top. I like lemon bars a little on the tart side.