A stove is a heated cooking surface and is definitely not period with the first stove being invented in the 18th century. However, it is impractical and impossible for any SCA cook to operate without one. At events in which a feast is prepared on site, modern ovens and stoves are used and are period by consensus, and rightfully so!
A portable stove is sometimes mentioned on the lists of camping gear to bring to camping events. These are also considered period by consensus for reasons of safety and convenience.