01 - Preheat oven to 350°F. Line a 9x13-inch baking dish with parchment paper or lightly grease it.
02 - In a medium bowl, combine the all-purpose flour, softened unsalted butter, and powdered sugar. Mix until the mixture becomes crumbly and resembles coarse sand. Press the crumbly dough evenly into the bottom of the prepared baking dish to form a uniform crust layer.
03 - Bake the crust for 18 to 20 minutes, or until the edges turn lightly golden. Remove from the oven and allow it to cool completely on a wire rack.
04 - Using an electric mixer, beat the softened cream cheese and powdered sugar together on medium speed until completely smooth and creamy. Gently fold in the whipped topping until well combined. Spread the cream cheese mixture evenly over the fully cooled crust using an offset spatula.
05 - In a large bowl, whisk together the instant lemon pudding mixes and cold milk for about 2 minutes until the mixture thickens. Stir in the lemon zest if using. Pour and spread the lemon pudding evenly over the cream cheese layer.
06 - Spread the remaining whipped topping gently and evenly over the lemon pudding layer, covering the entire surface.
07 - Cover the baking dish with plastic wrap and refrigerate for at least 2 hours, or until all layers are firmly set.
08 - Before serving, garnish with fresh lemon slices or additional lemon zest if desired. Cut into squares and serve chilled.