1. Position rack in the center of the oven and preheat the broiler.
2. In a bowl whisk together lemon juice and anchovy paste.
3. Gradually whisk in the oil.
4. Mix in tuna, celery, onion, basil, olives and capers.
5. Season with pepper.
6. Lightly toast both sides of bread on baking sheet under broiler.
7. When toasted, remove and rub one side of each slice with the garlic.
8. Cover each bread with a quarter of the tuna salad.
9. Top with cheese.
10. Melt under the broiler.