Preheat oven to 350 degrees. Spray with non-stick cooking spray a 9 x 13 baking dish.
Prepare spaghetti per instructions on back of package, drain and place back into pot and coat with 1 TBS of butter. Set aside.
In large bowl, mix together cooked chicken, soups, rotel or canned diced tomatoes, taco seasoning, and 1 cup of the cheese. Mix in the cooked, drained spaghetti. Pour mixture into prepared baking dish and spread evenly.
Cover with foil and place in preheated oven for 30 minutes. Uncover and sprinkle with remaining 1/2 cup of shredded cheese evenly. Place back into oven for 10-15 minutes until cheese has melted.
Let cool for 5 minutes. Garnish with fresh parsley, cilantro, or sliced green onions. Cut into squares. Serve and enjoy.