Jen's 'Famous' Veggie Spaghetti

This is my own recipe that I made up to be a little more healthy. We prefer it over spaghetti with meat in the sauce most of the time.
1 can tomato sauce
1 can tomato paste
1 can Italian style diced tomatoes
1 large garlic clove - crushed
1/2 cup green pepper - diced
1/2 cup onion - diced
1/2 cup black olives - chopped
1 can mushrooms (stems and pieces)
1/4 cup butter
Spices (I use Italian seasoning, Garlic salt, pepper, basil, oregano)

Melt 2 tbsp of butter in a large frying pan. Saute garlic, onion and pepper together in butter until tender. Add mushrooms, olives and tomatoes. Mix together and cook for about 5 minutes on medium heat. Add tomato sauce, paste, and spices. Mix together and then add spices to taste. Add remaining 2 tbsp of butter and simmer on medium low heat for about 10-15 minutes.
Serve over spaghetti noodles with parmesan cheese.