In a large frying pan melt the 1/2 stick of butter, cut the chicken into bite size pieces and saute in the butter.
When no longer pink inside add the chopped onions and chopped green pepper, I only cook the onion and green pepper for a couple minutes I like them a little crunchy. Your choice! Salt and pepper to your taste.
Boil spaghetti in a large pan of water. Cook according to the package. Drain the pasta after cooked and discard the water. DO NOT RINSE! Set cooked pasta aside.
Add the tomatoes, soup, and spaghetti to the sautéed chicken, onion and green pepper mixture and gently fold.
Add the cheese and stir together, mixing well add salt and pepper to your taste. Heat until cheese is thoroughly melted, but be careful not to BURN.