Preheat oven to 350 degrees F (175 degrees C). Grease an 8x8-inch baking dish with butter.
2
Beat eggs, sour cream, milk, and salt in a bowl until blended. Stir in green onions. Pour mixture in the prepared baking dish.
3
Bake in the preheated oven until set, 25 to 30 minutes. Sprinkle Cheddar cheese over eggs and continue baking until cheese is melted, 2 to 3 minutes more.