1. Preheat oven to 450°.
2. Combine first 3 ingredients in a small bowl; place tomato mixture on a foil-lined jelly-roll pan. Bake at 450° for 12 minutes or until tomato skins burst and begin to wrinkle, stirring once. Transfer tomatoes to a bowl, scraping juices into bowl. Stir 1/4 teaspoon salt into tomato mixture.
3. Place each chicken breast half between 2 sheets of heavy-duty plastic wrap; pound to 1/4-inch thickness using a meat mallet or small heavy skillet. Sprinkle chicken evenly with 1/4 teaspoon salt and pepper.
4. Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add chicken; cook 3 to 4 minutes on each side. Place chicken on individual plates; coat each breast half with 2 to 3 sprays of balsamic spritzer. Spoon tomatoes evenly over chicken.