To Prep
Let the rice cool down so that it is cold enough to handle. While waiting, cut the seaweed sheet into 4 long strips to wrap the onigiri with.
Drain any water or oil from the canned tuna, add the mayonnaise and pepper and mix well.
To Make the Onigiri
Wet your hands slightly with water and rub ½ tsp of salt in to them.
Place about a cup of rice into one hand and place a tablespoon of the tuna mayo into the centre.
Fold the rice over the tuna and begin shaping into a triangular shape.
Once the shape has been formed, wrap the onigiri in the seaweed strip and serve.