Heat oven to 350°F. Spray 8-inch square pan with cooking spray. Cook and drain pasta as directed on package.
In pan, mix pasta, chicken, frozen vegetables, soup and broth. Bake uncovered 35 to 40 minutes or until bubbly around edges.
Top with tomatoes. Sprinkle with onions and cheese. Bake uncovered about 3 minutes or until cheese is melted.