Preheat the oven to 375 degrees F. Grease a 9-x-13-inch glass baking dish and set aside.
In a medium bowl, mix butter, flour, powdered sugar and salt with a pastry cutter or spatula. Pat mixture into the prepared dish.
Bake for 20 minutes. Make sure to not let it brown.
While crust is baking, blend eggs, lemon juice, granulated sugar and flour in a medium bowl with a hand mixer until frothy, about 30 seconds. Pour over warm crust.
Bake for an additional 22–24 minutes. Bars are done when the edges begin to turn golden brown and the middle is set and does not wobble.
Let cool completely in the pan. Sift powdered sugar over the top before cutting into squares.
Make Ahead: These bars can be stored in an airtight container in the refrigerator for up to 7 days. Lemon Juice: Use freshly squeezed lemon juice. A medium-sized lemon will yield about 4 tablespoons of juice.