Completely drain the tuna. Transfer the tuna into a bowl and put the chopped cilantro with one teaspoon of mayonnaise into it. Mix the combination thoroughly.
In another bowl, slice the boiled egg and add one teaspoon of mayonnaise to it. Stir well.
Using a cutting board, chop the tomato, pepper, and avocado into small square pieces.
First, use the avocado as the base layer, then add the pepper on top of it, and then the tomato, followed by the egg mix. And lastly, place the tuna mix on top of the layers.
Serve and enjoy.