Preparation instructions from Apron Strings:
Slice your onion into 1/2 inch slices. Then, using the biggest one, place in an oiled skillet over medium heat. When one side is lightly browned, flip the onion ring over and crack an egg in the middle. If you want the egg yolk to show, dab the top of the egg yolk gently with a paper towel and remove the white over the top of it. Then, sprinkle a little water in the pan and cover the skillet. Cook until your egg is done as you like.If you don't care for onions, they also offer a way to cook eggs inside avocado slices.