Finely chop the red onion, tomatoes, coriander and jalapeños separately. Mix together the onion, tomatoes, coriander and a pinch of salt. Keep the jalapeños to one side.
Scoop all the avocado flesh into a bowl and crush with a fork, leaving it chunky – it should not be puréed.
Add the lime juice and onion mixture, combining gently.
Add jalapeños, to taste, and more sea salt if needed.
Serve with the tortilla chips.