Lightly spray a 9×13-inch baking dish with nonstick cooking spray.

Arrange a single layer of graham crackers at the bottom of the dish, breaking pieces to fit as needed.

In a large bowl, whisk together the lemon pudding mixes and cold milk for about two minutes until smooth and slightly thickened.

Gently fold the Cool Whip into the pudding mixture until fully combined and airy.

Spread half of the pudding mixture over the graham crackers.

Add another layer of graham crackers on top.

Spread the remaining pudding mixture evenly over this layer.

Place a final layer of graham crackers on top.

Microwave the lemon frosting (after removing the lid and foil) for about 30 seconds until soft and pourable. Stir until smooth.

Pour and spread the frosting evenly over the top graham cracker layer.

Cover the dish with plastic wrap and refrigerate for at least 12 hours, preferably overnight, to allow the layers to soften and set.

Slice into squares and serve chilled.