Preheat the oven to 425 degrees. Brush the turkey with the melted butter; season. Place skin side down on a rack in a roasting pan; pour the stock in the pan. Roast for 30 minutes.
Meanwhile, in a saucepan, cook the onion in the remaining 2 tbsp. butter over medium heat until soft, about 8 minutes. Add the cherries and syrup, chipotle, mustard and honey. Bring to a simmer, then remove from heat. Using a blender, puree 1/2 cup of the mixture.
Turn the turkey over; roast for another 30 minutes. Brush with the pureed cherry mixture; roast until an instant-read thermometer inserted into the thickest part registers 155 degrees, 10 minutes. Tent with foil and let rest for 15 minutes (the temperature will rise to 160 degrees).
Strain the pan juices into the reserved cherry mixture. Bring to a boil over medium-high heat and cook until thickened, about 2 minutes. Discard the turkey string. Slice crosswise; serve with the sauce.