• If needed, adjust oven racks so that sheet pan sits in upper-middle of oven. Preheat oven to 475° Fahrenheit.

For the Vegetables

• Rinse 12 ounces chopped broccoli florets under running water and drain well. Pat florets dry with paper towels then add florets to large mixing bowl and set aside.
• Rinse 12 ounces peeled baby carrots under running water and drain well. Pat carrots dry with paper towels then add to large mixing bowl with broccoli. Set aside.
• Rinse 1 pound red potatoes under running water, scrubbing gently to remove all surface dirt. Once potatoes have been rinsed, dry potatoes well with paper towels, then place potatoes on cutting board. Cut potatoes into 1-inch cubes, then add potatoes to bowl with broccoli and carrots.
• Peel 1 medium red onion and discard papery skin. Slice onion in half, then chop each half into ½-inch long pieces. Add chopped red onion to bowl with broccoli, carrots, and potatoes.
• Add 2 tablespoons neutral-flavored oil, salt, and freshly cracked black pepper to bowl, then toss all ingredients together until vegetables are well-coated in oil and seasonings. Set bowl aside.
  

For the Chicken

• Place 2 ½ pounds bone-in, skin-on chicken thighs on cutting board. Pat each chicken thigh completely dry on all sides with paper towels.
• Season each chicken thigh generously with salt and freshly cracked black pepper, then flip chicken thighs over and repeat. Set cutting board aside.
  

For the One-Pan Chicken & Vegetables

• Transfer vegetables to sheet pan and spread vegetables out into single, even layer, covering entire pan.
• Place chicken thighs skin-side up on top of bed of vegetables. Arrange chicken thighs as needed to minimize overlap.
• Place ½ cup unsalted butter in microwave-safe bowl and place bowl in microwave. Microwave butter in 30-second bursts, stirring well after each burst, until butter is melted but not boiling. Carefully remove bowl of melted butter from microwave.
• Add 6 cloves garlic, ½ teaspoon garlic powder, and 1 pinch salt to melted butter. Stir ingredients together until fully incorporated.
  
• Spoon approximately 50% of garlic butter sauce over chicken thighs, covering each chicken thigh evenly. If needed, depending on size of chicken thighs, use up to 25% more garlic butter sauce to cover chicken thighs. Reserve remaining garlic butter sauce.
  
• Place sheet pan in preheated oven. Roast chicken thighs and vegetables 15 minutes. After 15 minutes, carefully rotate sheet pan, then roast chicken and vegetables 15 minutes more.
• After 30 minutes total, insert internal meat thermometer into thickest area of chicken thighs to gauge doneness. If needed, return sheet pan to oven and roast chicken 5 minutes more, or until internal temperature reaches approximately 170° Fahrenheit. Be careful not to overcook vegetables.
• Once target internal temperature range is reached, carefully remove sheet pan from oven. Tent aluminum foil loosely over sheet pan to cover and set aside. Let chicken and vegetables rest, covered, 5 minutes.
  

To Serve

• After 5 minutes, remove aluminum foil and discard. Drizzle remaining garlic butter sauce over chicken thighs, then transfer chicken thighs to serving platter or plates.
• Season vegetables with additional salt and freshly cracked black pepper if desired, then toss vegetables in excess garlic butter sauce and pan juices.
• Once vegetables are well-coated, transfer. vegetables to serving platter or plates and serve immediately.