Cut the cucumber in half lengthways and scrape out the soft, watery centre if you prefer. Cut each half lengthways again, then chop into small pieces.
Thinly slice the spring onions and cut the radishes into small wedges. Put all the prepared vegetables into a mixing bowl.
In a small bowl, whisk together the miso paste, soy sauce, sesame oil, rice vinegar and lemon or lime juice. Taste and adjust the balance to your liking.
Pour the dressing over the vegetables, toss well and leave to marinate for about 10 minutes.
Meanwhile, boil the eggs if they are not already cooked. Peel and cut them into quarters.
Scatter the ground black cumin, sesame seeds and pumpkin seeds over the salad and toss gently.
Arrange the egg quarters on top and serve immediately.