Preheat your oven to 350°F degrees.
Grease the 9x13 inch baking dish well.
Slice yellow squash into thin, even pieces.
Dice the large onion into small pieces.
Cook squash and onion until very tender.
Drain excess water from cooked vegetables completely.
Mix sour cream with beaten eggs thoroughly.
Add cheese, salt, pepper, and garlic powder.
Combine squash mixture with creamy egg mixture.
Pour everything into the prepared baking dish.
Top with crushed crackers and melted butter.
Bake for 45 minutes until golden brown.