Dice the tomatoes, red onions into small pieces.

Dice the jalapeno into small pieces. If you do not wish for the dish to be as spicy, gut it of seeds first they produce most of the heat.

Cut up your cilantro if needed, Mix all four ingredients into a bowl.

Cut the lime in half, and squeeze juice using a fork into the bowl. Add salt to your taste. Stir. Congratulations, you just made pico de gallo.

Cut and scoop out the avocado into a seperate bowl or plate, removing the seed first. Mash the avocado you placed in a seperate dish using a fork or other utensil.

Add more salt, lightly... Combine your Avocado with the tuna and the pico de gallo.

Now you are done, so you should probably eat it, put it on bread or eat it alone. I really don't know what else you want.