Method

1. Place the tomatoes in a large bowl.
2. Cover with boiling water and let stand for 1 minute, and then lift out.
3. Using a knife, pierce the skin and peel it off.
4. Cut the tomato into quarters, cut out the central core and seeds.
5. Chop the remaining flesh and place in a large bowl.
6. Heat the oil in a skillet.
7. Chop the onion and gently fry until softened.
8. Add to the bowl of tomatoes with the mango and cilantro.
9. Season to taste with salt and pepper.
10. Serve cold with tortilla chips.