The root √AP appeared in The Etymologies of the 1930s as the basis for the words ᴹQ. apsa, N. aes “meat, cooked food” (Ety/AP). Tolkien glossed this root as “cook” which he marked with a “?”, then deleted the gloss (EtyAC/AP). Despite this deletion, I’ve seen a few Neo-Elvish writers use this root as the basis for verbs “to cook”, but I personally find this problematic as such forms tend to collide with Q. apta- “to refuse” < √BĀ/ABA. I prefer to retain the Early Qenya and Gnomish words maxa- and brath- for “to cook”.