Apex domains cannot have CNAME records.
Question and response
Question
dig a.akamaiedge.net. NS
Answer
a.akamaiedge.net. 5 NS n5a.akamaiedge.net.
a.akamaiedge.net. 5 NS n4a.akamaiedge.net.
a.akamaiedge.net. 5 NS n7a.akamaiedge.net.
a.akamaiedge.net. 5 NS n0a.akamaiedge.net.
a.akamaiedge.net. 5 NS n3a.akamaiedge.net.
a.akamaiedge.net. 5 NS n2a.akamaiedge.net.
a.akamaiedge.net. 5 NS n1a.akamaiedge.net.
a.akamaiedge.net. 5 NS n6a.akamaiedge.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0