Preheat your oven to 350°F (175°C). Move the rack to the center position. Lightly grease a 9x13-inch baking dish with nonstick spray or a thin layer of butter.

In a medium bowl, combine 1 1/2 cups all-purpose flour, 1/2 cup melted unsalted butter, 1/2 cup finely chopped pecans, 2 tablespoons powdered sugar, and 1/4 teaspoon salt. Stir with a fork until a crumbly dough forms, about 1–2 minutes. It should look like wet sand that clumps together when pressed.

Pour the dough into the prepared baking dish. Use your fingers or the flat bottom of a measuring cup to press it into an even layer across the entire bottom. Spend about 2–3 minutes getting it as uniform as possible — this ensures even baking.

Bake on the center rack for 16–18 minutes until the edges are light golden brown and the surface looks dry and set. It will feel slightly soft but will firm up as it cools. Checkpoint: You are ready to move on when the crust is completely cool to the touch — at least 30 minutes at room temperature. Do not rush this step.

In a large mixing bowl, beat 8 oz of softened cream cheese with a hand mixer or stand mixer on medium speed for 2 minutes until fluffy and smooth. There should be no lumps. Add 1 cup of powdered sugar and 1 teaspoon of vanilla extract, then beat for another 1–2 minutes until fully combined and silky.

In a separate chilled bowl, pour 1 cup of heavy whipping cream. Beat with a hand mixer on high speed for 2–3 minutes until stiff peaks form — when you lift the beaters, the cream should hold its shape without drooping.

Using a rubber spatula, gently fold the whipped cream into the cream cheese mixture in three additions. Use slow, sweeping motions from the bottom of the bowl upward to keep the mixture light and airy. Fold just until no white streaks remain.

Spread the cream cheese mixture evenly over the completely cooled crust using an offset spatula or the back of a spoon. Smooth it into an even layer. Checkpoint: You are ready to move on when the surface is flat and fully covers the crust.

In a large bowl, combine both packages of instant lemon pudding mix, 3 cups of cold whole milk, 2 tablespoons of fresh lemon juice, and 1 teaspoon of lemon zest. Whisk vigorously for 2 minutes until the mixture begins to thicken. It should be pourable but not runny — like a loose pudding.

Let the pudding rest for 3–4 minutes at room temperature to thicken slightly further, then pour and spread it evenly over the cream cheese layer. Work gently and quickly to keep the layers separate and clean.

Spread 1 1/2 cups of whipped topping over the pudding layer in an even, fluffy layer. Sprinkle 1 tablespoon of fresh lemon zest evenly over the top, then arrange thin lemon slices decoratively across the surface.

Cover the dish tightly with plastic wrap (do not let it touch the topping) and refrigerate for a minimum of 4 hours. For best results, refrigerate overnight — the layers will set firmly and the flavors will deepen. Checkpoint: You are ready to serve when the dessert is fully chilled and the pudding layer holds its shape when cut.