Combine the maple syrup, spiced rum, dark soy sauce, chili garlic sauce, minced ginger, cumin, minced garlic, and lemon juice in a bowl to make the sauce. Toss the chicken in this sauce sauce.
Preheat the oven to 400 degrees.
Layer the sliced onions along the bottom of the pan and lay the chicken over the onions skin side down.
Add the dissolved cornstarch to the sauce, stir well and pour over the chicken.
Sprinkle the chicken with fresh ground black pepper and sesame seeds and cook for 30 minutes.
Turn the chicken skin side up, glaze with the sauce in the pan and sprinkle with black pepper and sesame seeds, and cook for another 30 minutes.