Preheat the oven to 375°F.

Heat the oil in a heavy medium saucepan over medium heat. Add the onion and cook until translucent, about 5 minutes. Add the garlic and cook for 1 minute. Add the chiles and cook until darkened on both sides, about 1 minute.

Pour in the broth and bring to a boil. Cook until the chiles are soft, about 5 minutes. Transfer to a blender and puree until smooth. Season with salt and pepper.

Heat a large ovenproof grill pan over medium-high heat. Meanwhile, rub half of the adobo mixture all over the chicken. Sear the chicken, breast side down, until grill marks appear, about 6 minutes. Turn the chicken breast side up and transfer to the oven. Roast the chicken, basting with the remaining adobo sauce every 20 minutes, until an instant-read thermometer inserted registers an inner temperature of 180°F, about 40 minutes.