White Bean and Tuna Salad with Celery and Lemon

Serves:

• 1 (15-ounce) can cannellini beans, rinsed well and drained
• 2 (5-ouce) cans imported tuna in oil, drained and lightly flaked
• 2 celery ribs, thinly sliced plus 1/2 cup celery leaves from inner heart
• 1/2 cup very thinly sliced red onion
• 1 1/2 lemons
• 1/4 cup plus 2 tablespoons extra-virgin olive oil
• Coarse sea salt
• Mix of coarsely cracked black and white pepper
• 4 small radishes, very thinly sliced
• 1/2 small cucumber, very thinly sliced
• 1/2 cup whole flat-leaf parsley leaves