Apex domains cannot have CNAME records.
Question and response
Question
dig kayako.com. NS
Answer
kayako.com. 4 NS ns-1487.awsdns-57.org.
kayako.com. 4 NS ns-1727.awsdns-23.co.uk.
kayako.com. 4 NS ns-355.awsdns-44.com.
kayako.com. 4 NS ns-980.awsdns-58.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0