You have to kill 5 of them to complete the bestiary. Best way to kill them is using physical damage, but it's not a deal to finish this monsters.
You will find them, during the first stage of the world event A Piece of Cake (from February 21st to 26th), at Thais, Edron, Darashia, Carlin e Liberty Bay.
The Cake Golems spawn at different places, clicking here you can check a video of them at Edron.
Source: Tibiawiki.com.br; Emulov Sun channel at youtube.