01 - Preheat oven to 425°F. Line a baking sheet with parchment paper.
02 - Toss sweet potato cubes with olive oil, salt, and pepper. Arrange in a single layer on the baking sheet and roast for 25 to 30 minutes, stirring once midway, until caramelized and tender.
03 - Combine rinsed quinoa, water, and 1/2 teaspoon salt in a saucepan. Bring to a boil over medium-high heat, reduce to a simmer, cover, and cook for 15 minutes. Remove from heat and let stand for 5 minutes before fluffing with a fork.
04 - In a small bowl, whisk together tahini, lemon juice, water, olive oil, maple syrup or honey, garlic, salt, and pepper until smooth. Add more water if needed for desired consistency.
05 - Divide spinach or mixed greens among four serving bowls. Add portions of quinoa, roasted sweet potatoes, cherry tomatoes, red onion slices, and avocado to each bowl.
06 - Drizzle each bowl with lemon-tahini dressing. Top with crumbled feta, seeds, and fresh cilantro or parsley as desired. Serve immediately.