Halve the avocado and tap the stone with a sharp knife. Twist to remove the stone in one movement.
Repeat with the other avocados and scoop the flesh into a bowl. Add the lime juice and zest and mash with a fork. Set aside.
Place the coriander, spring onions, chillies and the tomatoes on a large wooden board and using a large knife, chop and combine the ingredients.
Fold into the mashed avocado. Season with black pepper. Garnish with more coriander.