01 - Preheat oven to 350°F. Lightly grease a 9x13 inch baking dish or line with parchment paper.
02 - In a medium bowl, combine flour, softened butter, and powdered sugar. Blend with a fork or pastry cutter until the mixture resembles coarse crumbs. Press firmly and evenly into the bottom of the baking dish.
03 - Bake for 18 to 20 minutes, or until the crust is lightly golden around the edges. Remove from oven and let cool completely.
04 - Using an electric mixer, beat softened cream cheese and powdered sugar on medium speed until smooth and creamy. Gently fold in the whipped topping until combined. Spread the mixture evenly over the cooled crust.
05 - In a bowl, whisk together both packages of instant lemon pudding mix and cold milk for about 2 minutes until thickened. Add lemon zest if using. Let the pudding sit for 5 minutes to fully set, then spread evenly over the cream cheese layer.
06 - Spread the remaining whipped topping evenly over the lemon pudding layer, smoothing the top with a spatula.
07 - Sprinkle lemon zest over the top for garnish, if desired.
08 - Cover and refrigerate for at least 2 hours, preferably 3 or more, until fully set. Slice into squares and serve chilled.