Preheat oven to 425F with rack in middle to an upper position.
Spray a large ovenproof skillet lightly with cooking spray. Pepper the chicken on both sides and position chicken skin side down in the skillet. (you can make up to 8 with this recipe – I was feeding 2 so I cut the chicken down to 4 but used the same amount of ingredients for the sauce.
In a medium size bowl mix together the vinegar, honey, soy sauce, ketchup, garlic powder, and red pepper flakes. Pour the mixture over the chicken in the skillet.
Bake chicken for 20 minutes, flip chicken skin side up, and continue baking until chicken browns on top (about 20 more minutes – internal temperature should be about 195 to 200F with an instant-read thermometer); transfer chicken to a serving platter.
Let the sauce in the skillet settle a little bit and spoon any excess fat off the top, or pour into a fat separator to separate the fat. In a small glass mix the cornstarch into the water until dissolved, place the skillet over a burner on medium high heat, bring mixture to a boil, and stir in the cornstarch mixture, cooking and stirring until thickened. Return chicken to the skillet, and roll the chicken in the sauce; garnish with the toasted sesame seeds.