Apex domains cannot have CNAME records.
Question and response
Question
dig scan-plus.com. NS
Answer
scan-plus.com. 5 NS ns3.scan-plus.com.
scan-plus.com. 5 NS ns5.scan-plus.com.
scan-plus.com. 5 NS ns4.scan-plus.com.
scan-plus.com. 5 NS ns2.scan-plus.com.
scan-plus.com. 5 NS ns1.scan-plus.com.
Authority
The response has no authority records.
Additional
ns1.scan-plus.com. 5 A 212.75.33.7
ns2.scan-plus.com. 5 A 212.211.130.7
ns3.scan-plus.com. 5 A 212.211.132.7
ns4.scan-plus.com. 5 A 18.221.110.61
ns5.scan-plus.com. 5 A 54.193.199.23
ns1.scan-plus.com. 5 AAAA 2001:a78:1:0:0:0:0:a
ns2.scan-plus.com. 5 AAAA 2001:a78:1:2:0:0:0:a
ns3.scan-plus.com. 5 AAAA 2001:a78:1:4:0:0:0:a
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0