In a spacious mixing bowl, combine the shredded chicken with ranch dressing until thoroughly coated. Fold in the crumbled bacon, diced tomatoes, finely chopped red onion, and fresh cilantro.

Grab a large flour tortilla and lay it flat. Sprinkle a generous layer of shredded Mexican cheese blend on half the tortilla, then spoon the chicken filling on top and add more cheese before folding the tortilla.

Heat a skillet over medium heat and melt a pat of butter. Once shimmering, place the folded quesadilla in the skillet and cook for 2-3 minutes until golden brown.

Carefully flip the quesadilla with a spatula and cook for another 2-3 minutes until golden and the cheese is melted. Press down with the spatula if necessary.

Transfer the quesadilla to a cutting board, let it cool for about a minute, then slice into wedges and serve with salsa or guacamole.