Preheat your oven to 350°F (175°C).

In a medium pot, bring water to a boil. Add your sliced yellow squash and cook for about 5 minutes until tender, then drain and set aside.

In a skillet over medium heat, melt a small amount of butter and sauté your chopped onion until soft and translucent, about 5-7 minutes.

In a large mixing bowl, combine the drained yellow squash, sautéed onions, shredded cheese, milk, eggs, salt, and pepper. Stir until well mixed.

Pour the mixture into a greased baking dish and top with the crushed crackers evenly.

Bake in the preheated oven for 30 to 40 minutes, or until the top is golden brown and the center is set.

Once removed from the oven, let the casserole rest for 5-10 minutes before serving.