Steps
1. Rinse the quinoa under cold water and combine it with 1 cup of water in a small pot. Bring to a boil, then reduce to a simmer and cover. Cook for about 15 minutes until the water is absorbed and the quinoa is fluffy.
2. While the quinoa cooks, heat the olive oil in a skillet over medium heat. Add the sliced onions and a pinch of salt. Cook for about 10-15 minutes, stirring occasionally, until the onions are golden brown and caramelized.
3. Add the spinach to the skillet with the onions and cook until wilted, about 2-3 minutes.
4. Season the onion and spinach mixture with black pepper, garlic powder, and balsamic vinegar. Stir to combine.
5. Fluff the cooked quinoa with a fork and serve it in a bowl topped with the caramelized onion and spinach mixture. Sprinkle with feta cheese if desired.