Pit your avocado,remove the stone,and scoop out the flesh. Mash it with a fork, sprinkle some salt and lemon juice
Fry your egg as you please
Butter your bread. Cut your onion into small pieces
Place the egg,followed by the avocado,tomato slices, and an egg layer. You can cover with another bread slice.
Alternatively,you can layer it as you fancy. Enjoy
Omit the egg if you wish too