Preheat the oven to 350°F.

Line a 9x13 baking pan with parchment paper or grease it with cooking spray or butter.

In a large mixing bowl, cut the butter into small squares.

Add flour, powdered sugar, and salt. Use a pastry cutter, 2 forks, or 2 knives to cut the butter into the flour mixture until it becomes coarse and crumbly.

Press the mixture evenly into the prepared pan, ensuring the edges are pressed tightly against the sides.

Bake for 20 minutes or until lightly golden brown. While the crust is baking, prepare the filling.

For the lemon filling, beat the eggs in a large mixing bowl with a mixer until slightly foamy.

Mix in the sugar, 1 cup at a time, then add the flour and mix well.

Add the lemon juice and zest, and mix thoroughly.

Remove the crust from the oven and pour the filling evenly over the warm crust.

Bake for 20 to 25 minutes or until the top is set and springs back lightly when touched. Avoid letting the top get too brown.

Remove from the oven and run a knife or spatula around the edges of the crust while still warm. Sprinkle sifted powdered sugar lightly over the crust, if desired, and allow it to cool.

For best results, refrigerate for at least 1 hour before cutting into bars. Keep refrigerated until ready to serve. Add additional powdered sugar before serving, if desired.