Pat the chicken dry and season generously with salt and pepper.
Whisk together melted butter, sugar-free syrup, vinegar, and cinnamon.
Brush the chicken generously with the glaze.
Roast 20 minutes, then reduce heat to 350°F (175°C) and continue roasting 35–40 minutes, basting with more glaze halfway through, until a thermometer in the thigh reads 165°F (74°C).