The grammar nazi strikes again. It's been awhile, but I haven't forgotten you.
A desert is a dry place with little rain.
A dessert is that sweet treat you have at the end of a meal.
How do you remember? Simple! A dessert is usually fattening. Dessert is a fatter word than desert.
So remember. The next time your characters want that sweet treat don't go sending them off into the Sahara, Gobi, or Atacama. Ain't no sweets there!