Spaghetti with Zucchini Sauce

1 medium onion, sliced
1/4 cup olive oil
2 medium zucchini, sliced
3 cups diced tomatoes
1/2 teaspoon salt
1 bay leaf
1/4 teaspoon pepper
1/4 teaspoon basil leaves
1/4 teaspoon oregano leaves
8 ounces spaghetti
Grated Parmesan cheese

In large skillet or pot, saut