01 - In a medium saucepan, combine the rinsed quinoa with water or vegetable broth. Bring to a rolling boil over medium-high heat, then reduce to a gentle simmer. Cover tightly and cook for 15 minutes until all liquid is fully absorbed. Remove from heat and let the quinoa rest, still covered, for 5 minutes. Fluff with a fork and spread on a sheet pan to cool to room temperature.
02 - Preheat a grill or grill pan over medium-high heat until thoroughly hot. Lightly brush the mango slices with olive oil on both sides. Place slices directly on the grill grates and cook for 2 to 3 minutes per side until distinct char marks appear and the fruit begins to caramelize. Transfer to a plate, allow to cool, then cut into bite-sized cubes.
03 - In a small mixing bowl, vigorously whisk together the olive oil, fresh lime juice, maple syrup or honey, ground cumin, chili flakes, salt, and black pepper until the dressing is fully emulsified and smooth. Taste and adjust seasoning as desired.
04 - In a large mixing bowl, combine the cooled quinoa, grilled mango cubes, diced red bell pepper, diced cucumber, finely chopped red onion, halved cherry tomatoes, chopped cilantro, and mint if using. Toss gently to distribute all components evenly.
05 - Pour the prepared citrus dressing over the assembled salad and fold gently with a large spoon or spatula until every ingredient is evenly coated. Taste once more and adjust salt, pepper, or lime juice as needed.
06 - Serve the salad immediately at room temperature, or cover and refrigerate for 30 minutes to allow the flavors to fully develop and meld together before serving.