Wash the lettuce, drain and cut into small pieces. Put in a salad bowl. Now add the tomatoes, walnuts and spring onions.
Core the avocados, remove the pulp from the skin and cut into small pieces. Drizzle with the lemon juice so that they keep their color. Pour into the salad bowl and carefully fold into the other ingredients.
For the dressing, put all the other ingredients in a blender jar with a lid and shake well. Pour over the salad and serve immediately. If necessary, season with salt and pepper.