*No cast iron skillet? You can use any oven safe skillet, though it will take a little longer - leave it on the burner for 5-7 minutes before putting in the oven.
You can skip the oven entirely, if you wish - after adding the eggs, stir gently to distribute cooked from the bottom. After 5 or 6 minutes, sprinkle cheese over the top, cover with a well fitting lid, and cook until the center is set, and the cheese is melted.