In a pot, combine quinoa with 2 cups of water. Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes until water is absorbed.

Remove from heat and let it sit covered for 5 minutes. Fluff with a fork.

Preheat the oven to 400°F (200°C).

Spread diced sweet potatoes on a baking sheet, drizzle with olive oil, and season with salt and pepper. Roast for 20 minutes or until tender.

In a mixing bowl, whisk together olive oil, apple cider vinegar, honey, Dijon mustard, salt, and pepper until well combined.

In a large bowl, combine cooked quinoa, roasted sweet potatoes, diced apple, and chopped spinach.

Pour the dressing over the salad and toss gently to combine.

Top with chopped walnuts and feta cheese if using.