Open each can of tuna, drain the juice and place the tuna in a large bowl. Grind the tuna slices well with a fork.
Cut the onion into very small squares and pour boiling water over it. Leave on for 5 – 7 minutes. After that, rinse the onions under cold water until they cool completely, leave the onions on a sieve so that all the water is in the insole. Squeeze the onion if necessary.
Cut green apples into small squares, having previously peeled and seeds removed.
Open a can of red beans, drain the liquid (you can rinse the beans).
Mix all ingredients in one bowl adding mayonnaise, salt and pepper. Adjust the amount of mayonnaise to suit your preference.