Wash and thinly slice the potatoes. Heat the oil in a non-stick frying pan, add the potatoes and cook over medium heat for 8 minutes until soft. Add the onions and fry for a further 3 minutes.
Stir in the olives and cherry tomatoes and season well with salt and freshly ground black pepper.
Beat the eggs in a bowl, then pour over the potatoes. Cook over a medium heat for 8 minutes until most of the egg has set. Then pop under a hot grill and cook for a further 4 to 5 minutes until the egg has set and is no longer runny.
Slip the omelette onto a plate, sprinkle with parsley and serve warm.