This cross between a no-bake cheesecake and a Key lime pie is a beautiful, light dessert for the lazy days of summer. Despite the dessert's title, don't feel you must use Key limes, which aren't always easy to find.
The larger, more common Persian limes will do a fine job on the flavor, and no one is likely to notice the difference. So what is the difference? See my note at the end of this post.