INSTRUCTIONS
1. Adjust oven rack to middle position and heat oven to 350 degrees. Combine chili powder, sugar, garlic powder, salt, pepper, and cumin in bowl. Sprinkle chicken all over with spice mixture.
2. Heat oil in ovensafe 12-inch skillet over medium heat until shimmering. Add chicken, skin side down, and cook until browned, about 5 minutes. Flip chicken and continue to cook until browned on second side, about 3 minutes longer. Transfer to plate.
3. Pour off all but 1 tablespoon fat from skillet and return to medium heat. Add onion and 2 tablespoons water and cook until onion is softened, 3 to 5 minutes, scraping up any browned bits. Stir in ketchup, molasses, Worcestershire, mustard, vinegar, liquid smoke, and remaining 2 tablespoons water and bring to simmer.
4. Return chicken to skillet and turn to coat with sauce. Flip chicken skin side up. Transfer skillet to oven and cook until breasts register 155 degrees or thighs register 170 degrees, 30 to 40 minutes for breasts or 20 to 25 minutes for thighs.
5. Remove skillet from oven and heat broiler. Broil until chicken is charred in spots and breasts register 160 degrees or thighs register 175 degrees, 2 to 5 minutes. Transfer chicken to platter and let rest for 5 minutes. Whisk sauce in skillet to recombine. Serve, passing sauce separately.