Put potatoes in medium pot and cover with 2 inches of water. Add pinch of salt. Bring to a simmer over medium-high heat and cook until just tender, 5-10 minutes. Drain and allow to cool to room temperature.
Bring water to a boil in medium pot to blanch green beans. Drop beans in boiling water and allow to cook for 1 minute. Drain beans and plunge in ice water to stop the cooking. The beans should still be crisp (al dente). When beans are cool, strain and lay on towel to absorb excess water.
Mix dressing ingredients. Adjust acidity to your preference and set aside.
Place romaine lettuce, red onion, radishes, tomatoes and yellow pepper in a large mixing bowl. Toss gently with ½ dressing. Season with fresh pepper. Place in the the centers of four large plates.
Place potatoes, French beans and tuna in mixing bowl. Toss gently with other ½ of dressing. Place in the center of the tossed vegetables.
Garnish salads with olives, sliced basil and a little drizzle of extra virgin olive oil.