Hm...
Spoiler contains definitions for 'lust' and 'tempt'.
So to test someone by offering them a choice of gaining something they want is not a sin? But if someone's 'want' is to strong it is labeled 'lust' and thus a sin?
Note that it is fully possible to lust for a hamburger, or for a good life. Just as it is possible to lust for bread (and water) in the desert, or for power over the whole world. At least according to definition 3 and 4.
Lusting can thus only be a sin if you lust for something that is considered sinful
and then give into the lust.
Thus, thinking of that hot girl, or wanting money, or planning to shoplift is not a sin, unless you actually act on those wants.
PS: I'm pretty sure you can think of your naked grandma and not give into your lust, so I don't think you actually consider thinking of naked people to be a sin.