Preheat your oven to 400°F.
Combine the maple mustard glaze ingredients in a small mixing bowl and set aside.
Use a sharp vegetable peeler to peel the butternut squash. Cut it in half, scoop out the inner seeds and guts, and then chop it into bite-sized pieces. Slice the red onion into thick slices.
Place the chopped butternut squash and onion in a large mixing bowl and drizzle with 2 tablespoons of extra virgin olive oil and toss to combine. Lightly season to your personal preference with kosher salt. Set aside.
Place the chicken thighs on a large baking sheet and pat dry with paper towels. Combine the 1 teaspoon of kosher salt, ¼ teaspoon of black pepper, and 1 teaspoon of garlic powder in a small bowl. Season both sides of the chicken thighs with the salt, pepper, and garlic powder mixture.
Spread about 75% of the maple mustard glaze (about 1 heaping teaspoon each) onto the tops of the chicken thighs. Set the remaining 25% aside and don't let it become contaminated with the raw chicken! When spooning the glaze onto the chicken, don't dip your spoon or brush back into the glaze after it's touched the raw chicken.
Transfer the baking sheet to the preheated oven and bake the chicken thighs for 10 minutes.
Remove the chicken from the oven, add the butternut squash and red onion to the baking sheet, and place everything back into the oven to continue cooking for 30-35 minutes. Cook until the chicken reaches an internal temperature of 175°F and the squash is fork-tender.
Once the chicken is cooked through, spread the remaining glaze onto the tops of the chicken and return the tray to the oven. (Only do this if you're positive you didn't contaminate your glaze with raw chicken germs!)
Broil under high heat for about 5 minutes or until the tops are golden brown.
Remove from the oven and let the chicken rest for about 10 minutes.
Serve and enjoy!