01 - Preheat oven to 350°F. Position the rack in the center of the oven.
02 - In a medium bowl, combine the flour, softened butter, and powdered sugar. Mix until the mixture becomes crumbly and well combined. Press the mixture firmly and evenly into the bottom of a 9"x13" baking dish.
03 - Bake for 18 to 20 minutes, or until the crust is lightly golden around the edges. Remove from the oven and let it cool completely.
04 - In a mixing bowl, beat the softened cream cheese and powdered sugar together until completely smooth and free of lumps. Gently fold in the whipped topping until evenly combined. Spread the mixture in an even layer over the cooled crust.
05 - In a large bowl, whisk together both packages of instant lemon pudding mix, cold milk, and lemon zest if using. Whisk vigorously for about 2 minutes until the pudding thickens. Spread 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 - Refrigerate the dessert for at least 2 hours, or until all layers are fully set and firm.
08 - Before serving, garnish with lemon slices or fresh lemon zest if desired. Cut into squares and serve chilled.