Cook yellow squash and zucchini separately in small amount of water for 5 minutes, drain well. Saute onion in bacon drippings until tender but not brown. Combine tomato sauce, chiles and salt, stir well.
Place yellow squash in 1 1/2 quart deep casserole, add onion spreading evenly, pour half of sauce over onion, add zucchini and pour remaining sauce over top.
Sprinkle with cheese and top with breadcrumbs. Bake at 350 degrees for 30 minutes until bubbly.
Note: Sometimes I do not add breadcrumbs, it is good either way.