Open the can of tuna, drain any liquid and transfer to a large mixing bowl. Break up the tuna into small pieces.

Add the mayonnaise and gently incorporate the ingredients together. Season to taste with salt and pepper then set aside.

Slice the bagel in half. Butter both the bottom and top slices of bagel (optional). Spread the bottom half of each bagel generously with some of the tuna mayo filling, and add a few slices of cheese across the bagel. Sprinkle a tiny amount of pepper on top (optional).

On a baking tray lined with parchment paper or foil, place both the bottom and top bagels onto tray (bottom half). Repeat step 3 for the same process for second bagel.

Transfer under the grill at a setting of 150 degrees. Cook for a few minutes until the cheese has melted on the bottom half of the filled bagel, and the top half of the bagel is lightly toasted golden brown. Turn off the oven and remove the bagels from the baking tray.

Transfer onto a plate, slice bagel in half if you wish and serve immediately while hot.