1.
In a large bowl, combine the tuna, halved cherry tomatoes, thinly sliced red onion, diced cucumber, sliced black olives, and greens. Finally, add the crumbled feta cheese.
2.
In a small bowl, mix the extra virgin olive oil with the lemon juice, Dijon mustard, salt, and pepper. Stir until emulsified.
3.
Pour the dressing over the salad and toss gently to coat all the ingredients.