Step 1

Arrange a rack in the middle of the oven, place a rimmed baking sheet on it, and heat to 500°F.

Step 2

Place the chicken, Parmesan, oil, garlic powder, salt, and pepper in a large bowl and toss to combine. Remove the hot baking sheet from the oven. Add the chicken and arrange into a single layer.

Step 3

Return to the oven and turn the heat down to 475°F. Roast for 10 minutes. Stir the chicken, add the asparagus and onion to the baking sheet in a single layer, and return to the oven until the chicken is cooked through and the onion and asparagus are tender, 6 to 10 minutes more.