Desert, as a noun, is an arid place with little vegetation or something deserved or merited, especially a punishment.
- The Southwest desert ranges are beautiful places to visit.
- When the plan was revealed, they received their just deserts.
- Despite financial setbacks, he refuses to desert the company.
Dessert, the noun, is the sweet thing one eats at the end of a meal.
- After dinner, we usually stop at the bakery for dessert.