Whenever I have brought a new adult cat home, I do the same thing I do with kittens - gently put kitty into the litter box, take their front paws and do the 'scratching' motion in the litter. Since cats do that in the wild, they should catch on.

Even a full tom can usually get that, you might have to do it once or twice.

Pepper could have done it out of nervousness too - new place. And if he is not neutered yet, that is how tomcats mark their territory - pee!

I swear by the 'litter box training' - it's never failed me.

hugs
Catty1