Spray a large nonstick skillet with cooking spray. Place skillet over medium-high heat until hot.
Spread Ranch dressing evenly on 1 side of each tortilla. Place 1 tortilla, dressing side up, in hot skillet; top evenly with half each of cheese, bacon, and tomato. Lightly press a second tortilla, dressing side down, on top of mixture. Coat lightly with cooking spray, and cook 1 to 2 minutes on each side or until golden.
Repeat procedure with remaining tortillas, cheese, bacon, and tomato.
Cut each quesadilla into wedges. Serve with Ranch dressing and salsa.