When I was about twelve I was really into Egyptology, and the Amarna period in particular. Akhenaten's reign and its fallout are at the same time highly iconic (King Tut's Mask and Nefertiti's bust) and very different from the rest of Ancient Egypt. I decided to read up on it again (mostly Wikipedia), and apparently there have been a few major discoveries in recent years. Obviously after Akhenaten's dead odd things happened (Tut had to change his name for religuous-political reasons, he died young and was succeeded by his advisor Ay) but apparently a lot more happened as well.
A female pharaoh named Neferneferuaten reigned between the two, and she was apparently both Nefertiti, the Dakhamunzu of the Zannanza affair, and the original owner of Tut's golden mask. And it seems like another pharaoh named Smenkhkare reigned somewhere during this period, too.
Who was this Smenkhkare? What does the latest research on the topic say about the period between Akhenaten's death and Tutankhamun taking over?
My information mostly comes from The Rise and Fall of Ancient Egypt by Toby Wilkinson. He mentions that the last historical record of Nefertiti is in Akhetaten after the death of her children. It is possible the Nefertiti also died at this time. However, it is also possible that she became coregent and then took the name Neferneferuaten. If this is the case it is also possible that after the death of Akhenaten she herself became sole ruler and took the name Smenkhkara. She and her followers would have wanted to continue the religous revolution that her husband started. It is also possible that Smenkhkara could be a son of Akhenaten that we are otherwise unaware of. With the religous reforms being removed soon after Tut took the throne it is likely much of the historical record was erased. I'm sure the priest of Amun would have loved for this period of history to be forgotten completly! So without further evidence being uncovered we may never know for sure.
That said the book is 7 years old so hopefully someone with more knoweldge and access to better sources will comment, as I myself will love to learn more about this period!