Rinse and Toast Grains: Thoroughly rinse the quinoa in a fine-mesh sieve under cold running water. Shake off excess water. Place the quinoa in a dry 2-quart pot over medium heat. Toast for 3-4 minutes, stirring constantly, until the grains are dry and smell nutty.
Simmer the Quinoa: Pour the water into the pot with the toasted quinoa. Increase heat to medium-high to bring to a boil. Reduce heat to medium-low, cover with a tight-fitting lid, and simmer for 12-15 minutes until the liquid is absorbed.
Fluff and Cool: Remove from heat and let stand, covered, for 10 minutes. Uncover, fluff gently with a fork, and spread onto a plate or baking sheet to cool down.
Awaken Aromatics: While the quinoa cooks, combine the diced red onion, minced garlic, lemon juice, lemon zest, white balsamic vinegar, sumac, and black pepper in the bottom of a wide mixing bowl. Whisk briefly and let sit. This maceration step softens the onion's bite and infuses the acid with flavor.
Toast the Seeds: In a small, dry skillet over medium-low heat, toast the sunflower seeds for 2-3 minutes, tossing frequently until golden. Remove immediately to prevent burning.
Assemble the Salad: Whisk the olive oil into the lemon juice and onion mixture in the large bowl to complete the vinaigrette. Add the cooled quinoa, rinsed chickpeas, cucumber, bell pepper, dill, and mint. Toss well to coat every grain.
Rest and Serve: Refrigerate for at least 15 minutes to allow flavors to marry. Stir in the toasted sunflower seeds just before serving for maximum crunch.