Halve the avocados and tap the stones with a sharp knife. Twist to remove the stones in one movement and scoop the flesh into a bowl. Add the lime juice and zest and mash with a fork. Set aside.
Finely chop the coriander, tomatoes, spring onions, garlic and chillies and combine. Fold into the mashed avocado and season with black pepper. Garnish with more coriander to serve.