Cook beef, onions and butter until brown. Then drain out the fat.
Stir in the tomatoes and chili. Let it simmer for 45 mins. Then remove from heat.
Meanwhile cook the spaghetti. Drain and set aside.
Once the pan is done simmering and is removed from heat, stir in grated cheese until melted. Fold in sour cream.
Mix with cooked spaghetti. Spoon into 4 or 5 quart casserole dish. Sprinkle with Parmesan cheese.
Cover the dish. Bake at 350' for 45 minutes.