Using a quesadilla maker, place a tortilla on burner and add chicken, cheeses and tomatoes. Add filling to center and leave at least 1" around ends because the cheese melts and will run.
Cook for 2-3 minutes until quesadilla is golden brown and edges are sealed. Remove and cut.
If you don't have a quesadilla maker, put filling on one half on tortilla and fold over. Then cook on skillet over medium heat on each side for about 2 minutes.