وتر رکعت
the correct view about qunoot is that it can be done at any prayers. It has been reported that Prophet Mohammad saw has prayed qunoot due to calamity at various times including in fajar. Witr is part of Tahajjud as evident from this hadith https://sunnah.com/muslim/6/192 If you pray tahjjud then its better to pray witer at that time. However, if you cannnot wakeup then according to this hadith https://sunnah.com/muslim/6/195 you can pray after isha. Thats the reason for offering witr after isha Kindly correct me if i am wrong