Slice the onion thinly.
Prepare the ham and cheese.
Beat the eggs, add a pinch of salt, and mix well.
Add oil to a pan and sauté the onions.
Add the ham and stir-fry together.
Push the cooked ingredients to one side of the pan, pour in the egg mixture, and scramble.
Spread butter on one side of a bread slice.
Place the bread on the pan and layer cheese, ham, scrambled eggs, and onions in order.
Cover with another slice of bread and press lightly with a sandwich press or spatula while toasting.
Toast both sides until golden brown and serve.