Tuscan Tuna and White Bean Salad

In a bowl, combine beans, red onion, tuna, tomatoes, olives, parsley, 2 tablespoons of the reserved olive oil, lemon juice, lemon zest, salt, and pepper, tossing gently to combine. Stir in arugula. Preheat grill or heat grill pan. Brush flatbreads lightly with the remaining reserved olive oil. Grill until lightly browned, about 2 minutes per side. Cut flatbreads in halves or quarters. Serve with salad.