In Dutch oven, cook sausage over medium-high heat 5 minutes, stirring frequently; drain. Add onions, bell pepper and garlic; cook and stir 4 to 6 minutes or until bell pepper is tender.
Stir in remaining ingredients except spaghetti. Reduce heat; simmer 20 minutes.
Meanwhile, cook spaghetti as directed on package; drain.
Remove bay leaf from sauce. Serve sauce over spaghetti. Sprinkle with grated Parmesan cheese if desired.