Place the oil in a non stick skillet over medium heat, add the onions and saute until translucent. Add the garlic and ginger, and cook for 2 minutes. Add the tomato sauce and cumin seeds, cook for one minute and reduce the heat to low.
Add the garam masala, brown sugar, pepper flakes, turmeric, salt, lemon juice, and cook for 2 minutes.
Add the chicken and cook until it is nearly done. Add the milk and simmer until the chicken is cooked through, 3-5 minutes. Serve over rice.