You can also use yellow squash for this...or a combo of both.
1/4 cup butter, plus another tablespoon to dot with
1 cup shredded cheddar cheese
1/2 cup sour cream
1/2 - 1 teaspoon salt (to taste)
1/4 cup finely diced/minced onion
1 cup dry bread crumbs
1/2 cup - 1 cup Parmesan cheese, depending on taste
Do not peel zucchini; just wash and cut ends off. Cut into quarters; put in large pot and bring to boil. Boil 8-10 minutes, or until almost tender; drain well. Transfer drained zucchini to 9x13 baking dish. Melt butter in medium sized, microwave-safe bowl. Stir in cheese, sour cream, salt and onion. Pour over zucchini. Dot with remaining butter. Shake/pour breadcrumbs over entire mixture; sprinkle with Parmesan cheese. Bake at 350 degrees for 20-25 minutes. Cheese should be lightly browned.