When my mother was in college, she would have dinner at a friend's house on occasion. Her friend's mother made this dish quite often when she would come. Mothers always asked her for the recipe, but she always refused to give it to her. When my Mother and Dad married, she did finally give her the recipe. The reason for the absence of meat in the recipe is because it was during WWII when meat was being rationed.
Preheat oven @ 300 degrees. Cook the spaghetti according to the directions on the box. Chop and saute onion in melted butter until golden. Drain the spaghetti and onion. Place in a dish sprayed with Pam. Add cubed cheese and tomatoes. Mix all ingredients. Cook for 3 hours @ 300 degrees. Check after 2 hours. My family likes the top crispy, so we leave it in the oven longer. Make sure you leave it in the oven long enough for all the cheese to melt. Also, I usually triple the recipe because everyone in my family loves it, so it does take 3 hours the more spaghetti and cheese you use. If you are a cheese lover like we are, I add at least a half a pound more cheese than what it calls for.