Apex domains cannot have CNAME records.
Question and response
Question
dig flexiconf.com. NS
Answer
flexiconf.com. 2 NS ns1.iptox.net.
flexiconf.com. 2 NS ns2.iptox.net.
flexiconf.com. 2 NS ns3.iptox.net.
Authority
The response has no authority records.
Additional
ns1.iptox.net. 5 A 95.128.200.4
ns2.iptox.net. 5 A 116.202.87.218
ns3.iptox.net. 5 A 95.128.200.7
ns1.iptox.net. 5 AAAA 2a00:1200:0:1:0:0:0:aa
ns2.iptox.net. 5 AAAA 2a01:4f8:10b:4354:0:0:0:2
ns3.iptox.net. 5 AAAA 2a00:1200:0:1:0:0:0:bb
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0