Rinse the quinoa under cold water to remove any bitterness. In a saucepan, combine the quinoa and water or vegetable broth. Bring to a boil, then reduce heat and simmer for 15-20 minutes, or until the quinoa is cooked and the liquid is absorbed. Remove from heat and let it cool.
In a large bowl, combine the cooked quinoa, cherry tomatoes, cucumber, bell pepper, red onion, parsley, mint, feta cheese (if using), Kalamata olives, and toasted pine nuts.
In a small bowl, whisk together the lemon juice, extra virgin olive oil, salt, and pepper. Pour the dressing over the quinoa salad and toss to combine.
Taste and adjust the seasoning if needed. You can add more lemon juice, olive oil, salt, or pepper according to your preference.
Serve the quinoa salad chilled or at room temperature. It can be enjoyed as a side dish or a light meal on its own.