Everyone loves this recipe! Don't skimp on butter or parmesan cheese. I made this one time without frying squash first and didn't use butter, there wasn't any buttery juices which make this casserole. A crowd pleaser and worth the calories!
Slice onion into thin slices and then each slice into 4.
Slice tomatoes in half then each half in half and then in half again.
Mix the squash together with the onion and fry on medium heat using 4 tablespoons butter for each batch; I do 4 batches, 1 at a time so you don't overload frying pan; make sure not to brown the squash, cook about 5 minutes each batch, add quarter of tomatoes and mix.
Layer vegetable in a single layer in a large casserole dish that has been sprayed with Pam. Coat the top of vegetables with 4 oz. parmesan cheese, repeat layers ending with parmesan cheese.
Cover and bake in a 350 oven for 2 hours or until squash is done.