Drain the oil from the tuna into a medium bowl. Add the chickpeas and toss to coat.
In a large salad bowl, toss together the lettuce and arugula.
In a small bowl, whisk together the pesto, lemon juice, 1/4 tsp salt and the cayenne.
Just before serving, toss the greens with the dressing and divide among 4 plates. Top with the tuna, chickpeas, olives and tomatoes. Serve with the lemon wedges.