Bring a large pot of salted water to a boil. Add zucchini and cook until tender, about 15 minutes; drain. Scoop out the flesh of the zucchini, making a boat.
In a medium bowl, combine the zucchini flesh, bread crumbs, cheddar cheese, onion, parsley, salt, most of the Parmesan cheese and egg. Fill zucchini boats with the mixture. Drizzle with melted butter and sprinkle with remaining Parmesan cheese.
Bake in preheated oven for 30 minutes.
Recipe by Sports Mom Survival Guide at https://www.sportsmomsurvivalguide.com/stuffed-zucchini/