1. Trim onion halves so they sit upright. Scoop out centers, leaving 1/2-inch shells. Chop onion from centers to equal 2 cups and reserve.
2. Place onions, cut-side up, in baking pan; add water to half of the height of the onions. Cover and bake in a 400° oven for 40 minutes or until onions are fork tender. Drain well.
3. Saute chopped onions, pepper, zucchini, mushrooms, and pine nuts in oil. Add tomato paste, wine seasonings and tomatoes. Simmer until blended and tender. Fill each onion half with about 1/4 cup shredded cheese; place 2 halves in each of 4 individual baking dishes or bake all in large dish. Bake, covered, in a 425-degree oven for 20 to 25 minutes or until thoroughly heated.