Apex domains cannot have CNAME records.
Question and response
Question
dig airsmail.com. NS
Answer
airsmail.com. 5 NS a14-65.akam.net.
airsmail.com. 5 NS a1-199.akam.net.
airsmail.com. 5 NS dns4.p01.nsone.net.
airsmail.com. 5 NS a18-66.akam.net.
airsmail.com. 5 NS a28-64.akam.net.
airsmail.com. 5 NS dns1.p01.nsone.net.
airsmail.com. 5 NS a9-67.akam.net.
airsmail.com. 5 NS a5-66.akam.net.
airsmail.com. 5 NS dns2.p01.nsone.net.
airsmail.com. 5 NS dns3.p01.nsone.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0