In a large skillet, combine soups, chicken broth, and tomatoes and heat until bubbly. Spray a 9x13-inch casserole dish with cooking spray.
Layer half of tortilla chips, half of chicken, half of onion, and half of cheese in the casserole dish. Pour half of chicken broth moxture over layers. Repeat layers of tortillas, chicken and onion, then pour remaining chicken broth over top. Top with the remaining cheese.