Clean and wash all the vegetables. Slice the cabbage into thin strips, massage them a little so to make them softer. Place in a large bowl.
Dice the cucumber, tomatoes and red onion to a similar size. Add to the bowl.
Chop finely the fresh cilantro and parsley. Add to the bowl together with the olives.
In a small container with a lid add all the dressing ingredients and close tightly. Shake the container vigorously until the dressing is combined.
Add the dressing to the salad and mix everything well. Top the salad with the mixed seeds and sumac. Let the salad rest for at least 30 minutes before serving.