In a small bowl, mix together the tomatoes, onion, jalapeno, coriander. Season with salt and pepper. Cover with cling film and set aside for 1 hour. Serve with tortilla crisps.
For the tortilla crisps:
1) Pour the oil into a large heavy-bottomed pot to a depth of about 5-cm. Place a deep-frying thermometer in the pot. Heat the oil over medium heat to 182C.
2) Meanwhile, stack the tortillas, and cut the pile into sixths to make crisps.
3) Raise the heat to high. Working in batches, fry the crisps, turning them with a skimmer or slotted spoon, until golden brown, about 2 minutes. Using a slotted spoon, transfer the crisps to a kitchen towel-lined pan to drain. (Return the oil to the proper temperature between batches.) Cool and season with salt. Serve.