Apex domains cannot have CNAME records.
Question and response
Question
dig portunity.com. NS
Answer
portunity.com. 5 NS ns3ac.portunity.com.
portunity.com. 5 NS ns4ac.portunity.com.
portunity.com. 5 NS nset1.portunity.com.
Authority
The response has no authority records.
Additional
ns3ac.portunity.com. 5 A 192.174.68.100
ns4ac.portunity.com. 5 A 176.97.158.100
nset1.portunity.com. 5 A 188.246.0.33
nset1.portunity.com. 5 A 217.144.128.33
ns3ac.portunity.com. 5 AAAA 2001:67c:1bc:0:0:0:0:100
ns4ac.portunity.com. 5 AAAA 2001:67c:10b8:0:0:0:0:100
nset1.portunity.com. 5 AAAA 2a02:a00:0:0:0:0:0:a1
nset1.portunity.com. 5 AAAA 2a02:a00:f:0:0:0:0:a2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0