Tuna and White Bean Salad - Fresh-Pressed Olive Oil

Ingredients

• 3 cups cooked white beans, such as cannellini or Great Northern beans, drained and rinsed if canned
• 1 cup diced celery hearts plus a few celery leaves for garnish
• 1 red bell pepper, stemmed, seeded, and diced
• 1 small red onion, finely sliced crosswise
• 1 clove garlic, finely minced
• 15 to 20 pitted brine-cured kalamata olives, halved
• 2 tablespoons minced flat-leaf parsley
• 4 to 5 tablespoons extra virgin olive oil
• 2 tablespoons fresh lemon juice or red wine vinegar, or more to taste
• Sea salt and coarsely ground black pepper
• Head of romaine lettuce
• 12 ounces tuna, either fresh and seared or the highest-quality canned, flaked