Cook the macaroni to package directions. If you have room in your pot, you can cook the green beans with the macaroni. Add a tsp of chicken bouillon powder to the water to flavor the noodles and green beans.
In a 9x13 inch baking dish, combine the macaroni, tuna, and soup. Mix well, and then top with cheese.
Bake at 350 degrees F for about 15 minutes, or until bubbly. Sprinkle with fried onions, and bake for another 5 minutes. Serve hot.
