In a medium saucepan, combine the quinoa, water and 1/2 teaspoon sea salt. Bring to a boil over high heat. Reduce heat, cover and simmer for 15 minutes, until the water has been absorbed. Spread quinoa on a cookie sheet and allow to cool, about 30 minutes.
Once quinoa has cooled, transfer to a large bowl. Add tomatoes, olives, feta, sunflower nuts, onion and parsley. Toss to combine.
In a small bowl, whisk together the olive oil, lemon juice, dijon mustard, garlic, the 1/4 teaspoon sea salt and black pepper.
Pour lemon dressing over the quinoa salad and toss. This salad can be served immediately, or covered and refrigerated to serve later.