1 acorn squash (about 1 1/2 lb), halved, seeded and cut into 1/2-inch- thick slices
1 tbsp olive oil
1 red onion, cut into 1/2-inch wedges
3/4 tsp each sea salt and ground black pepper, divided
4 large boneless chicken thighs (about 1 lb), trimmed
3 tbsp pure maple syrup
1 1/2 tbsp finely chopped fresh rosemary
1 tbsp coarsely chopped garlic
Preheat oven to 375°F. In a large bowl, toss squash with oil; spread in a single layer on a large rimmed parchment-lined baking sheet. Arrange onion wedges around squash. Sprinkle 1/4 tsp each salt and pepper over vegetables. Bake for 15 minutes.
Meanwhile, in same bowl, toss chicken with maple syrup, rosemary, garlic and remaining 1/2 tsp each salt and pepper.
Increase oven temperature to 425°F. Place chicken on same baking sheet on top of squash and onions. Pour any remaining syrup mixture from bowl over chicken. Return to oven and bake until an instant-read thermometer inserted into the largest thigh registers 165°F, 25 to 30 minutes. Baste chicken once or twice during baking time using juices from bottom of baking sheet.