Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Peel and dice the butternut squash into uniform 1/2-inch cubes and place them on one side of the prepared baking sheet.
Place the chicken breast on the other side of the sheet and season both the chicken and squash with olive oil, half the sea salt, black pepper, and garlic powder.
Toss the squash cubes to ensure they are evenly coated and spread them out in a single layer to ensure they roast rather than steam.
Roast in the oven for 20-25 minutes until the chicken reaches an internal temperature of 165°F and the squash is tender and slightly caramelized.
While the tray roasts, combine the dry quinoa and water in a small saucepan over high heat and bring to a boil.
Reduce the heat to low, cover the saucepan, and simmer for 15 minutes until the water is absorbed and the quinoa is fluffy.
Remove the chicken from the oven and let it rest for 5 minutes before slicing it into thin, bite-sized strips.
In a large serving bowl, create a base with the fresh baby spinach and warm quinoa, then top with the roasted squash and sliced chicken.
Whisk together the lemon juice and the remaining salt, pepper, and garlic powder to create a light dressing and drizzle it over the bowl.
Finish the dish by sprinkling crunchy pumpkin seeds over the top for added texture and healthy fats.