Apex domains cannot have CNAME records.
Question and response
Question
dig vixie.org. NS
Answer
vixie.org. 3 NS jokulsa.asbyrgi.net.
vixie.org. 3 NS fj0rd.vixie.org.
Authority
The response has no authority records.
Additional
fj0rd.vixie.org. 3 A 24.104.150.234
jokulsa.asbyrgi.net. 3 A 24.104.150.234
fj0rd.vixie.org. 3 AAAA 2001:559:8000:cd:0:0:0:6
jokulsa.asbyrgi.net. 3 AAAA 2001:559:8000:0:0:0:0:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0