Zucchini Cheese Bake

I don't know what to call this, "Zucchini Cheese Bake"?  Except that you don't really bake it, you broil it... Whatever its called, my dad made it up and its delicious!  The key to this recipe is using lots of butter and garlic salt.

3-4 zucchini and summer squash
onion, chopped
1 can diced tomatoes
mozzarella cheese, shredded
garlic salt (lots!)

Saute onion in butter until tender (use 1/2 a stick or more).  Add sliced zucchini and summer squash, cover with garlic salt and cook.  Add tomatoes when the zucchini is almost done, along with more garlic salt.  Let this all cook for a few minutes longer, then transfer to an 8x8 dish.  Cover with shredded mozzarella cheese and more garlic salt.  Broil just until cheese browns.  Serve over noodles or as a side dish.