Rinse the quinoa thoroughly in a fine-mesh strainer to remove excess saponin, which can make the cooked grains taste bitter. Combine the rinsed quinoa, water or vegetable broth, and 1/2 teaspoon salt in a saucepan.

Bring the quinoa mixture to a boil, then reduce the heat to low and cover the saucepan. Simmer for about 15 minutes, or until the liquid is absorbed and the quinoa grains have opened.

Remove the saucepan from the heat and let the quinoa stand, covered, for 5 minutes. Fluff it gently with a fork, then spread it on a shallow tray or plate so it can cool completely.

Whisk together the olive oil, lemon juice, minced or grated garlic, remaining 1/2 teaspoon salt, and black pepper in a small bowl. Taste the dressing and adjust only if needed before adding it to the salad.

Place the cooled quinoa, parsley, mint, tomatoes, cucumber, and scallions in a large bowl. Pour the dressing over the mixture and toss gently until the grains and vegetables are evenly coated.

Refrigerate the salad for at least 20–30 minutes so the flavors can blend. Taste just before serving and adjust with more lemon juice, salt, or olive oil as needed.