Broccoli Rice Casserole

Preheat oven to 350 degrees. Coat the inside of a 1 1/2 quart baking dish with cooking spray. Place the oil in a large skillet over medium heat. Add the onion, celery and bell pepper and cook about 8 minutes until softened, stirring frequently. Stir in the soup and sour cream and heat through. Remove the skillet from the heat. Later the rice and chopped broccoli in the prepared dish. Pour the soup mixture over the layers and spread evenly. Cover and bake the casserole 20 minutes. Uncover and top with the tomato slices. Bake the casserole an additional 10 minutes. Serve the casserole hot.