Bring a pot of water to a boil and cook the eggs for seven minutes, so the yolk is still slightly soft in the center. Shock them in cold water and peel them.
In the same water, cook the green beans for four minutes until tender-crisp and bright green. Drain and immediately rinse them with cold water, otherwise they will continue to cook and lose their color and bite.
Whisk the olive oil with the mustard, red wine vinegar, salt, and pepper into an emulsified dressing.
Arrange the little gem lettuce on a large plate and arrange the green beans, halved cherry tomatoes, drained tuna in large chunks, and halved eggs in groups on top. Sprinkle with the olives and capers, spoon the dressing over everything, and finish with roughly chopped parsley. This classic from Nice combines two complete protein sources with plenty of vegetables and contains barely any carbohydrates.