I must say, I prefer spaghetti squash with a brown butter sauce and garlic rather than a tomato sauce.
A really good (and surprising) 0-carb spaghetti substitute is shredded and steamed cabbage... no kidding it really works. Once the cabbage is steamed (for about 5 mintues in water and a pinch of salt) it loses it's flavor making it perfect with tomato sauce.
Also good is zucchini and/or eggplant made into a lasagna with tomato sauce. Yum.
