Preheat oven to 350 degrees F.
In a small bowl, beat the egg.
In a large mixing bowl, mix the melted butter and cubed bread. Toss the bread to coat.
Add in the egg, zucchini, onion, and garlic sea salt. Mix well.
Transfer this mixture to a 9x13 inch backing dish and top with 1 cup of the shredded cheddar cheese.
Bake covered in a preheated oven for 30 minutes. Then, uncover the dish, top with the remaining cup of cheese and bake for an additional 30 minutes.
Serve.