Prepare the crust: Combine flour, sugar, and nuts. Cut in softened butter until mixture resembles coarse crumbs. Press into the bottom of a 9x13 inch baking dish.
Make the cream cheese layer: Beat cream cheese and sugar until smooth. Add lemon zest and juice; mix well. Gently fold in thawed whipped topping.
Prepare the pudding layer: In a separate bowl, whisk together instant pudding mix and cold milk until smooth and thickened. Let it sit for a few minutes to set slightly.
Assemble the cake: Spread the cream cheese mixture evenly over the crust. Top with the pudding layer, spreading it evenly.
Add the top layer: Spread the remaining thawed whipped topping over the pudding layer.
Chill: Refrigerate for at least 2 hours to allow the cake to set completely.
Garnish: Before serving, garnish with lemon zest and lemon slices.
Notes
This recipe can be made ahead of time and stored in the refrigerator for up to 3 days.