Step 1

Preheat oven to 375°F and grease a 9x13-inch baking dish with nonstick spray.

Step 2

Place onions in a saucepan and add water just to cover. Bring to a boil, reduce heat and let simmer 8 minutes. Drain and toss onion slices with butter.

Step 3

In a large bowl, whisk together eggs and evaporated milk. Add cooked onions, cracker crumbs, cheese, salt, and pepper. Stir to mix.

Step 4

Transfer to baking dish. Toss together cracker crumbs and melted butter for topping. Sprinkle over casserole.

Step 5

Bake until set in the center and top is golden brown, about 45 minutes. Enjoy!