Apex domains cannot have CNAME records.
Question and response
Question
dig vcn.com. NS
Answer
vcn.com. 5 NS ns2.vcn.com.
vcn.com. 5 NS ns1.vcn.com.
vcn.com. 5 NS ns3.vcn.com.
Authority
The response has no authority records.
Additional
ns1.vcn.com. 5 A 209.193.72.114
ns2.vcn.com. 5 A 209.193.68.3
ns3.vcn.com. 5 A 209.193.68.3
ns1.vcn.com. 5 AAAA 2607:f498:4001:0:0:0:0:3
ns2.vcn.com. 5 AAAA 2607:f498:4501:0:0:0:0:3
ns3.vcn.com. 5 AAAA 2607:f498:4501:0:0:0:0:3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0