Peel the potatoes, wash them, cut them into cubes, and boil them.

Peel the onion, cut it in half and then into thin slices. Wash and finely chop the lettuce and parsley. Drain the capers.

In a large bowl, layer the lettuce, drained potatoes, onion, parsley, and capers. Add plenty of salt and pepper, vinegar, and olive oil, then toss to combine.