Apex domains cannot have CNAME records.
Question and response
Question
dig sp.actionkit.com. NS
Answer
sp.actionkit.com. 5 NS ns-1315.awsdns-36.org.
sp.actionkit.com. 5 NS ns-1821.awsdns-35.co.uk.
sp.actionkit.com. 5 NS ns-369.awsdns-46.com.
sp.actionkit.com. 5 NS ns-690.awsdns-22.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0