Apex domains cannot have CNAME records.
Question and response
Question
dig demysdns.net. NS
Answer
demysdns.net. 5 NS ns0.demysdns.net.
demysdns.net. 5 NS ns3.demysdns.net.
demysdns.net. 5 NS ns1.demysdns.net.
demysdns.net. 5 NS ns5.demysdns.co.uk.
demysdns.net. 5 NS ns6.demysdns.co.uk.
demysdns.net. 5 NS ns2.demysdns.net.
demysdns.net. 5 NS ns4.demysdns.co.uk.
Authority
The response has no authority records.
Additional
ns0.demysdns.net. 5 A 198.51.44.11
ns1.demysdns.net. 5 A 198.51.45.11
ns2.demysdns.net. 5 A 198.51.44.75
ns3.demysdns.net. 5 A 198.51.45.75
ns4.demysdns.co.uk. 5 A 198.51.44.19
ns5.demysdns.co.uk. 5 A 198.51.45.19
ns6.demysdns.co.uk. 5 A 198.51.44.83
ns0.demysdns.net. 5 AAAA 2620:4d:4000:6259:7:11:0:1
ns1.demysdns.net. 5 AAAA 2a00:edc0:6259:7:11:0:0:2
ns2.demysdns.net. 5 AAAA 2620:4d:4000:6259:7:11:0:3
ns3.demysdns.net. 5 AAAA 2a00:edc0:6259:7:11:0:0:4
ns4.demysdns.co.uk. 5 AAAA 2620:4d:4000:6259:7:19:0:1
ns5.demysdns.co.uk. 5 AAAA 2a00:edc0:6259:7:19:0:0:2
ns6.demysdns.co.uk. 5 AAAA 2620:4d:4000:6259:7:19:0:3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0