Drain and rinse beans, mix together with onion, salsa, and cheese.
Spread 1/2 mixture on tortilla in large skillet, heat tortilla until cheese starts to melt and tortilla starts to brown. Slide tortilla out of skillet onto plate, put another tortilla on top, hold skillet upside down over plate and turn tortilla back into skillet. Heat tortilla until cheese starts to melt and tortilla starts to brown. Cut with pizza cutter. Make second tortilla.