Blend onion, ginger, soy sauce, salt, oil, wine, and vinegar.
Pour this mixture over and inside the chicken; marinate for at least 1 hour.
Preheat oven to 425°F.
Place the chicken (breast side up) and marinade in a baking tray.
Roast for 1.5 hours or until the thickest part of the thigh reaches 165°F.
While roasting, dissolve brown sugar, lemongrass, and water in a saucepan over medium heat (about 5-8 minutes) until it thickens slightly.
Once the chicken is golden brown and fully cooked, pour the glaze on top.
Let rest for 20 minutes before serving.