Preheat the oven to 350°F (175°C). Grease a 9x13-inch casserole dish with butter or non-stick spray.

Melt 3 tablespoons of butter in a large skillet over medium heat. Add the sliced squash, diced onion, and 1/2 teaspoon of salt. Sauté until the squash is tender and the onions are soft, about 8-10 minutes. Drain the excess liquid from the skillet.

In a large mixing bowl, whisk together the eggs, sour cream, cheddar cheese, mayonnaise, black pepper, garlic powder, paprika, cayenne pepper, and the remaining 1/2 teaspoon of salt.

Gently fold the cooked squash and onion mixture into the egg and cheese mixture until everything is evenly combined.

Pour the squash mixture into the prepared casserole dish, spreading it out evenly.

In a small bowl, mix the crushed Ritz crackers with the melted butter until the crumbs are coated. Sprinkle the cracker mixture evenly over the top of the casserole.

Bake for 25-30 minutes, or until the topping is golden brown and the casserole is bubbling around the edges.

Let the casserole cool for 5 minutes before serving. Enjoy!