Rinse the quinoa at least twice in cold water and drain in a sieve. Bring the water to the boil in a saucepan. Add a pinch of salt and the quinoa. Wait for it to return to boiling, cover and simmer over very low heat for 15 minutes. Drain, use a fork to loosen fluff up the grains and set aside.
Put the diced cucumber in a sieve and sprinkle with salt. Let it drain for 20 minutes. Rinse with cold water, drain again and set aside.
Place tomatoes, onion and feta in a bowl. Add the diced cucumber, quinoa, sprouts and coriander. Toss.
In a separate bowl, prepare the vinaigrette. Whisk the lime juice, vinegar and olive oil. Season with salt and pepper and pour over salad. Toss again and adjust the seasoning if necessary.