In a large skillet over medium heat, melt 2 tablespoons of butter. Once bubbly, add 4 cups of sliced yellow squash and 1 cup of chopped onion. Sauté for 8-10 minutes until the squash is tender and slightly translucent.

Remove the skillet from heat and let the sautéed vegetables cool slightly. In a mixing bowl, combine the sautéed squash and onion with 1 cup of sour cream, 1 cup of shredded cheddar cheese, 1 teaspoon of garlic powder, and 1 teaspoon of onion powder. Season with salt and pepper to taste.

Preheat your oven to 350°F. Grease a 2-quart baking dish with cooking spray or a little butter, then transfer the creamy vegetable mixture into the prepared baking dish.

In a small bowl, mix 1 cup of crushed butter crackers with 1 tablespoon of melted butter. Evenly sprinkle this mixture over the top of the casserole. Bake for 25-30 minutes, or until the topping is golden brown.

Once baked, remove the casserole from the oven and let it cool for about 5 minutes before serving.