Fast, easy, and good. When tomatoes are at their summer best this is a must at our house, or for any luncheon, church dinner, or just to pass some on to neighbors, which I do, since there is just my husband and I at home.
Cook macaroni and cheese and prepare as directed on box.
Chop the green onions and dice the tomato, saving the juice and adding it to the dish. Toss the macroni and cheese, onion, and tomato with the mayonnaise. Add more if needed. I have also added 1/4 cup sour cream to this instead of more mayo.
Enjoy - soooo good.