Cook eggs: Place the eggs into a saucepan, cover well with water, and bring to a boil. Remove from the heat and let stand, covered, for 13 minutes. Drain and place into a bowl of iced water. Let stand for about 5 minutes. Peel.
Make filling: Halve and carefully remove the yolks. Place the egg yolks into a bowl and mash them with a fork. Add the avocado and mash with a fork again, mixing well. You can use a blender for a smoother consistency.
Chop vegetables: Halve the tomato and remove its seeds. Chop the tomato very finely. Chop the spring onions very finely as well. Keep about 1 tablespoon of the chopped greens of the spring onions for sprinkling over the eggs when ready to serve. Grate the garlic clove.
Combine filling: Add tomatoes, spring onions and garlic to the bowl together with a pinch of lime zest, the juice of half a lime, pure chili powder or cayenne pepper to taste, ground coriander, ground cumin, salt, and pepper to taste as well. Add more lime juice if necessary.
Add herbs: Finely chop the fresh coriander or parsley. Fold about ⅔ of the herbs into the mixture.
Stuff the egg white halves with the filling. Place on a serving platter and sprinkle with the remaining herbs, some chili powder or cayenne pepper, finely chopped greens from the spring onions, and finely chopped radishes, if desired.
Keep refrigerated until ready to serve. They are best served shortly after being prepared.
Notes
For easy peeling, the eggs should not be super fresh. Ideally, they should be 10 days old.