Heat a dry skillet over medium-low heat. If desired, heat with a bit of oil added.
Place the tortilla in the pan.
Cover the half surface of flour tortillas with cheese and any of your other favorite fillings.
Fold your flour tortilla's empty side over the filled side.
Cook until the cheese has melted and the bottom tortillas are golden and crispy, pressing both together with your spatula.
Flip the tortilla and cook for a minute or two on the other side.
Transfer to a work surface and cut into slices.
Clean the pan and repeat the process to make another quesadilla.
Serve with salsa, guacamole, and/or sour cream if desired.