Photograph: Dan Jones
Rinse the quinoa and simmer, part covered, in 600ml boiling water for 15 minutes until tender; drain and cool.
Mix the dressing ingredients.
Chop the watercress, kale and spinach. Mix with the quinoa, all the other ingredients and the dressing; season.
Kitchen secret: sumac is a red, lemony-tasting Middle Eastern spice – you will find it alongside the other spices in the supermarket.