We had this at a friends cookout yesterday.  I loved it and had to get the recipe.  Its super easy.

1 oz. pkg cream cheese (room temp)

1 cup milk (I used soy milk)

1 (4 serving) box of lemon pudding/pie filling mix

Beat with mixer until smooth, then fold in 1 cup of Sugar Free Cool Whip, and 2 tsp lemon zest. I bought a graham cracker crust but use what ever one you want.  Then top with 1 cup of cool whip on top and put in fridge for at least 3 hours or overnight.