Apex domains cannot have CNAME records.
Question and response
Question
dig vivo. NS
Answer
vivo. 5 NS a.nic.vivo.
vivo. 5 NS ns2.dns.nic.vivo.
vivo. 5 NS c.nic.vivo.
vivo. 5 NS ns1.dns.nic.vivo.
vivo. 5 NS b.nic.vivo.
vivo. 5 NS ns3.dns.nic.vivo.
Authority
The response has no authority records.
Additional
a.nic.vivo. 171403 A 37.209.192.9
b.nic.vivo. 171403 A 37.209.194.9
c.nic.vivo. 171403 A 37.209.196.9
ns1.dns.nic.vivo. 171403 A 156.154.169.57
ns2.dns.nic.vivo. 171403 A 156.154.170.57
ns3.dns.nic.vivo. 171403 A 156.154.171.57
a.nic.vivo. 171403 AAAA 2001:dcd:1:0:0:0:0:9
b.nic.vivo. 171403 AAAA 2001:dcd:2:0:0:0:0:9
c.nic.vivo. 171403 AAAA 2001:dcd:3:0:0:0:0:9
ns1.dns.nic.vivo. 171403 AAAA 2610:a1:1071:0:0:0:1:39
ns2.dns.nic.vivo. 171403 AAAA 2610:a1:1072:0:0:0:1:39
ns3.dns.nic.vivo. 171403 AAAA 2610:a1:1073:0:0:0:1:39
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0