Eggplant and Black Bean Stew

1 large onion, chopped (1 cup)

1 medium green bell pepper, cut into 1-inch pieces

2 cups 1-inch pieces eggplant (3/4 pound)

1/2 cup water

1/4 teaspoon salt

1 medium zucchini, cut lengthwise in half, then cut crosswise into 1/4-inch slices (2 cups)

2 cans (14 1/2 ounces each) diced tomatoes with basil, garlic and oregano, undrained

1 can (15 ounces) black beans, rinsed and drained

Shredded Parmesan cheese, if desired