1 egg, lightly beaten
1 cup mayonnaise
1/8 teaspoon ground black pepper
3 cups finely shredded Cheddar cheese
1 onion, finely chopped
Preheat oven to 325 degrees F (165 degrees C). Spray a 1-quart baking dish with cooking spray.
In a bowl, mix the egg, mayonnaise, and pepper. Stir in the Cheddar cheese and onion, and transfer to the prepared dish.
Bake 25 minutes in the preheated oven, until golden brown.