Chop the onion, put it in a bowl and sprinkle it with salt so that it will soften. (You can also press and mix it with the salt so that it softens faster)

Add the canned tuna and mix it with the onion wih a spoon.

Add the corn. (I used a small can)

Peel and chop the avocado and add it to the mix.

Season to taste. I used some olive oil with basil, yum!