Step 1 For the dressing, whisk all the ingredients together and set aside in a flat dish.
Step 2 Cook beans in boiling water for 2 minutes, drain and cool.
Step 3 Brush both sides of tuna with olive oil and season with freshly ground black pepper. Place tomatoes in a bowl and spray with cooking spray. Spray bread on both sides with cooking spray.
Step 4 Place cooked beans, lettuce leaves, olives, red onion and basil in a large bowl and mix until well combined.
Step 5 Heat barbecue or chargrill on high heat, reduce to medium and cook tuna for 2 minutes each side, adding an extra minute if too rare. Cook tomatoes until skins split (about 5 minutes), turning occasionally.
Step 6 Toast bread on barbecue or grill for about 2 minutes each side, until golden. When bread is toasted, remove from heat and rub 1 side with garlic half.
Step 7 When tuna and tomatoes are cooked, place in dressing and leave for 5 minutes. Remove tuna. Add tomatoes and dressing to salad. Stir to combine. Divide salad between plates, top with tuna and serve with bread on the side.