Boil sufficient water in the deep vessel and blanch the tomatoes for three minutes.
Peel, deseed and chop the tomatoes finely. Cut the avocado in half, remove the pit, scoop the flesh and place them in food processor and process until smooth.
Transfer the process avocado into a bowl, add in chopped tomatoes, lemon juice, onion, garlic, coriander leaves, green chillies and salt and mix. Serve cold with tortilla chips