Combine half the cheese and 1/4 cup tomatoes. Make horizontal cut in 1 long side of each chicken breast to make pocket, being careful to not cut all the way through to opposite side of breast. Spoon cheese mixture evenly into chicken pockets; press cut sides of breasts together to seal pockets. Place in 13x9-inch baking dish sprayed with cooking spray. Brush with 2 Tbsp. dressing.