Finely chop the onion, season with salt and ground black pepper, and pour a generous amount of lime juice.
Add the olive oil and mix.
Drain the juice from the tuna and mash the fish pieces with a fork.
Lay it out to the onion.
Add finely chopped coriander to the tuna.
Add the tomato, peeled from the seeds and cut into small pieces.
Stir well.
Try the appetizer, if necessary add salt, pepper or lime juice and put in the refrigerator for 30 minutes.
You can serve it on toast, bread, wrapped in pita bread, etc. (I have chips).