Preheat the oven to 350°F (175°C).

In a large skillet over medium heat, sauté the chopped onion until it’s translucent, about 5 minutes. Add the sliced yellow squash and continue cooking for another 5-7 minutes until tender.

In a large mixing bowl, combine the softened yellow squash and onion, cornmeal, shredded cheese, beaten eggs, and milk. Season with salt and pepper, and mix until well combined.

Coat a 9x13-inch baking dish with butter or oil.

Transfer the squash mixture into the greased baking dish, spreading it evenly. Bake in the preheated oven for about 30-35 minutes, or until set and golden brown on top.

Let it cool for a few minutes before serving.