1Add oil to skillet on medium high heat and sauté onions for a couple minutes. Turn heat down to medium. Start toasting muffins. Move onions to side of pan and add butter and crack in the eggs. After 2 minutes add a slice of cheese over each egg.
2Cook everything until egg whites have set (about 2 or 3 minutes more).
3When muffins are done spread one side of each with mayo and mustard. With a spatula place eggs onto the muffins and the onions over the eggs.
4Now with the pan empty add the slices of salami to the pan and fry for about 1 minute each side. Place the salami over the onions and your sandwich is done.