01 - Combine quinoa, water, and 1/4 teaspoon salt in a saucepan. Bring to a boil, reduce heat to low, cover, and simmer for 12 to 15 minutes until all water is absorbed. Remove from heat, fluff with a fork, and allow to cool completely.
02 - Preheat grill or grill pan over medium-high heat. Lightly brush cut sides of nectarine halves with olive oil. Place nectarines cut side down on the grill and cook for 2 to 3 minutes until charred and caramelized. Flip and grill for an additional 1 to 2 minutes. Remove from heat, let cool slightly, then slice into wedges.
03 - In a small bowl, whisk together olive oil, lemon juice, honey or maple syrup, Dijon mustard, salt, and black pepper until emulsified and smooth.
04 - In a large serving bowl, combine cooled quinoa, arugula, cucumber, red onion, chopped mint, and parsley. Drizzle with the prepared dressing and toss gently to coat evenly.
05 - Arrange grilled nectarine wedges over the salad. Sprinkle with crumbled feta cheese and toasted almonds or pistachios. Serve immediately, or refrigerate for up to 2 hours to allow flavors to meld.