In a mixing bowl, combine shredded cooked chicken with ranch dressing, ensuring each piece is coated well. Then, fold in the crumbled bacon, diced tomatoes, finely chopped red onion, and fresh cilantro if using.

Place a large skillet over medium heat and add a generous pat of butter, allowing it to melt and coat the bottom of the pan.

Lay a flour tortilla flat on a clean surface and sprinkle a layer of shredded Mexican cheese on one half. Spread a generous amount of the chicken filling over the cheese, followed by another layer of cheese. Fold the tortilla in half.

Carefully place the folded quesadilla in the heated skillet and cook for 2-3 minutes on one side, until golden-brown. Flip and cook the other side for an additional 2-3 minutes.

Once both sides are beautifully golden, remove the quesadilla from the skillet and let it rest on a cutting board for a minute. Use a sharp knife to cut it into wedges.

Plate your chicken bacon ranch quesadilla wedges and consider serving them with a side of guacamole or fresh salsa for dipping.