Preheat the oven to 375°F. Line the bottom of a large pan with a rack with aluminum foil [for easy clean-up] or spritz an oven safe grill pan or broiler pan with cooking spray.
Rinse and pat dry the chicken pieces. Drizzle the chicken pieces with olive oil then rub liberally with the seasoning on all sides. [Seasoning: BBQ seasoning and brown sugar]
Place skin side down on the rack or pan. The skin will crisp when the chicken is basted and turned. Bake for 30 minutes.
While the chicken is baking, on the stovetop saute the minced onion in 1 Tbsp of butter. Saute until softened, around 2-3 minutes. Add the remaining ingredients and simmer on low uncovered for 15 minutes to reduce and thicken. Skip this if using a prepared barbecue sauce.
After the chicken has baked for 30 minutes, remove from the oven and drain the juices from the pan.
Drizzle the chicken with sauce. Turn and drizzle the top with sauce.
Bake for another 10-15 minutes or until the juices run clear. If the breast pieces are large, remove the wings, back and legs to a platter at 40 minutes and keep warm.
Continue to cook the breast pieces checking in 5 minute increments, until the juices run clear or the chicken has reached an internal temperature of 165°F.
To char: At the end of cooking, increase the oven temperature to broil, and move the oven rack up. Broil the chicken for 3-4 minutes until the skin is charred. Keep a close eye on the chicken. Remove from the oven, brush with sauce and rest loosely tented with foil for 10 minutes before serving.
Serve leftover sauce on the side, if desired.