01 - Preheat a large skillet or griddle over medium heat until evenly hot.
02 - Place one tortilla on a clean surface. Sprinkle about 3/4 cup shredded cheese evenly over half of the tortilla, then add your choice of optional fillings. Fold the tortilla over to create a half-moon shape.
03 - Place the filled tortilla onto the hot skillet. Cook for 2-3 minutes, pressing gently with a spatula, until the tortilla is golden brown and crispy.
04 - Flip the quesadilla carefully and cook for another 2-3 minutes until the second side is golden brown and the cheese is completely melted.
05 - Remove from heat and transfer to a cutting board. Let cool for 1-2 minutes, then cut into 3-4 wedges.
06 - Repeat with remaining tortillas and fillings. Serve immediately with sour cream, salsa, guacamole, and fresh cilantro on the side.