Place the potatoes in a medium saucepan, covering them with cold water.
Add salt, cover, and bring to a simmer over low heat.
Cook for about 15 minutes or until the potatoes are tender when pierced with a knife.
Drain and let them cool slightly.
Peel and cut into 1-inch pieces.
In a large bowl, gently fold together the cooked potatoes, slivered onion, orange pieces, and pimiento.
In a small bowl, whisk together the red wine vinegar and extra-virgin olive oil.
Pour the dressing over the salad and gently fold it in.
Season with salt and freshly ground black pepper to taste.