Apex domains cannot have CNAME records.
Question and response
Question
dig twdcns.com. NS
Answer
twdcns.com. 5 NS ns6.twdcns.co.uk.
twdcns.com. 5 NS ns3.twdcns.info.
twdcns.com. 5 NS ns4.twdcns.info.
twdcns.com. 5 NS ns1.twdcns.com.
twdcns.com. 5 NS ns2.twdcns.com.
twdcns.com. 5 NS ns5.twdcns.co.uk.
Authority
The response has no authority records.
Additional
ns1.twdcns.com. 5 A 193.108.91.64
ns2.twdcns.com. 5 A 204.74.66.147
ns1.twdcns.com. 5 AAAA 2600:1401:2:0:0:0:0:40
ns2.twdcns.com. 5 AAAA 2001:502:f3ff:0:0:0:0:293
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0