Cook the green beans is boiling water or steam them for 3-5 minutes, then transfer them to ice-cold water. Drain and put them in a serving bowl.
Cut the tomatoes in half, add to the beans.
Finely chop the spring onions and scatter these on top of the salad together with the coriander leaves.
Peel the avocado, remove its stone, then cut the flesh into small cubes. Immediately squeeze half of the lime over them and toss well.
Arrange the avocado pieces on top of the salad. Drizzle with oil and the remining lime juice. Season with salt and pepper to your liking, then serve.