To slice the potatoes into almost transparent slices.
To cut up the sweet onion.
Put the Extra Virgin Olive oil into the pan( South Spain recomended one(Specially from Jaén)
Mix everything (Potatoes+ onion + salt) into a frying pan ( Pirex one is the best because content will never stick on the base) Olive oil should completelly cover the potatoes.
Fry it all in a very low frame, itis necessary to have it arround 25-30mtos ( Till you will see potatoes are completelly soft) From minute 15, move the content with a wooden spoon every 3-5 minutes to create the final paste of soft potatoes)
When paste is finish, take the content out from the pan an put it on a recepip where eggs have previously been mixed. Remove the Olive oil from the pan
Mix the paste with the eggs smoothly and put it on the pan again (low frame as well) Have it about 3-4 minutes and ,helping you with a plate which will cover the pan, turn over the omelette.
Repeit this action as much as you prefer the interior egg cooked (For me is 2 times each side)
As presentation sugerence, after you have it on your plate, you can cut it into squared pieces!
Fresh white wine "Manzanilla" ( From South of Spain)