Some clarification: A desert – a barren land. A dessert is a delicacy after a meal.
‘Just deserts’ means “that which one deserves”, and it is spelled with one S, but pronounced like the after-meal word.
The word “desert” also means payback, but it is generally not used in that sense in isolation. It has nothing whatsoever to do with dessert.
As a play on words, you will sometimes see the phrase “just desserts” referring to a restaurant, the idea being that you deserve the great food, but this is a pun and has nothing to do with the actual meaning of the word.
PBA is obviously aware of this but as other people are mixing up the terms in this thread, I thought it would be worthwhile to make it explicit.