1. Cook the quinoa: In a saucepan, bring the water to a boil. Add the quinoa, reduce heat to low, cover, and simmer for 15 minutes. Remove from heat and let it sit, covered, for 5 minutes. Fluff with a fork.
2. Grill the asparagus: Preheat the grill to medium-high heat. Toss the asparagus with 1 tablespoon of olive oil, salt, and pepper. Grill for 5-7 minutes, turning occasionally, until tender and slightly charred. Cut into bite-sized pieces.
3. Assemble the salad: In a large mixing bowl, combine the cooked quinoa, grilled asparagus, cherry tomatoes, and feta cheese.
4. Dress the salad: Drizzle with the remaining 1 tablespoon of olive oil and lemon juice. Toss to combine. Season with additional salt and pepper to taste.
5. Serve: Serve the salad warm or chilled.