Wash the fresh baby spinach and dry it thoroughly in a salad spinner. Finely chop the red onion. Drain the tuna in a colander or sieve and press out any excess water firmly.
Place the eggs in a saucepan and add cold water until they are completely submerged. Bring the water to a boil and cook the eggs for nine minutes from that point. Drain the water, plunge the eggs immediately under cold running water and peel them once they have cooled.
Whisk the extra virgin olive oil and fresh lemon juice together in a small bowl to make a smooth dressing. Season to taste with salt and freshly ground black pepper. Mix the dry spinach, finely chopped red onion and tuna in a large bowl. Pour the dressing over it and toss everything well.
Divide the mixed salad among the plates. Cut the peeled eggs into wedges and place on the servings. Serve immediately.