Place the potatoes (skin on) in a large pot. Cover with cold water, add a pinch of salt, and bring to a boil.
Boil the potatoes for 20–25 minutes, or until they are tender when pierced with a fork.
Meanwhile, place the eggs in a saucepan and cover with boiling water. Cook for 10 minutes.
Drain the eggs and rinse under cold running water until they’re cool. Peel and set aside.
Wash the tomato, green bell pepper, and onion. Dice the tomato and pepper into bite-size pieces; finely chop the onion. Drain the tuna thoroughly.
Once the potatoes are cool enough to handle, peel and cut them into medium dice. Transfer to a large bowl.
Add the chopped tomato, bell pepper, onion, olives, and flaked tuna to the bowl.
Cut the cooked eggs into quarters or slices and add them to the salad.
In a small bowl, whisk together the extra-virgin olive oil, white wine vinegar, and salt to taste.
Pour the dressing over the salad and gently toss until everything is evenly coated.
Cover the bowl with plastic wrap and refrigerate for at least 30 minutes before serving.