Preheat the oven to 350°F. Prepare a 9x13-inch casserole dish with a light coating of nonstick spray.
In a large bowl, whisk together the eggs, sour cream, and melted butter until smooth. Stir in the drained corn and undrained cream corn until well combined.
Fold in the Jiffy mix, cayenne pepper, 3/4 cup of the cheddar cheese, and most of the green onions. Season to taste with salt and pepper.
Spread the mixture evenly in the prepared dish. Top with reserved cheese and green onions if desired.
Bake for 45-55 minutes until golden brown and set. The edges should be lightly browned, and a toothpick inserted in the center should come out mostly clean.
Remove from the oven and let rest for at least 10 minutes. Slice and serve warm.