- 15 minutes
- 5 minutes
- Heat broiler, with rack in highest slot. Mix tuna, mayonnaise, onion, capers, lemon juice, salt, pepper, and oregano in a medium bowl and stir until well blended.
- Place bread on a baking sheet and coat each slice with a little mayonnaise. Distribute tuna salad evenly among slices, and then add 2 slices tomato and 1 slice cheese to each. Broil for 3 to 4 minutes, or until cheese is golden brown and bubbling.