Finely slice the onion.
Heat some oil in a frying pan and gently cook the onion over low heat for about 8 minutes.
Meanwhile lightly whisk the eggs in a small bowl with two pinches of salt.
When the onion is soft and lightly brown, transfer it to a plate.
Add another spoonful of oil to the pan, turn up the heat and pour in the eggs. Let them spread out.
When the egg has almost set on the surface, scatter the cheese all over it. Let the cheese melt, then scatter around the cooked onion and some herbs.
Fold the omelette in half and cook for another minute over low heat, then slide it onto a plate.
Serve with a green salad and some wholesome bread, with some fresh herbs scattered on the top.