In a medium bowl, whisk together oil, lemon zest and juice, salt, pepper, and chives. Add parsley leaves, beans, tuna, and onions and stir gently just until coated.
Arrange tomato slices on 4 plates and spoon tuna mixture on top, dividing evenly. Top each salad with a few parsley leaves if you like.
*Look for pole- or troll-caught.
Note: Nutritional analysis is per serving.