Use light mayo and low fat cheese for a lower fat version.
Cut the bagel in half and grate the cheese. Then, drain the tuna and mix with mayo and pepper in a bowl.
Preheat the grill to medium heat (about 160° C).
Pop bagel halves in toaster and toast until very lightly browned, spread tuna & mayo on to the bagel halves and sprinkle with the grated cheese.
Place under the grill until cheese has melted nicely. Plate up and sprinkle with crispy onion bits. Serve.
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