Finely chop or mince red onions and add them to the bowl.
Finely chop the chili pepper and add it to the mixture. Adjust the amount based on how spicy you want the salad to be.
Add the drained tuna and break it up into small flakes using a fork. If you're using tuna with sunflower oil, you may leave some of the oil as well, for taste.
Peel the hard-boiled eggs and chop them into small pieces. Add them to the bowl.
Add mayonnaise, salt, and pepper to the bowl. Mix all the ingredients together until well combined and coated in the mayo.
Notes
The best way to serve this salad is to put it on the bun with some extra Iceberg salad. Enjoy!