Apex domains cannot have CNAME records.
Question and response
Question
dig btsaas.net. NS
Answer
btsaas.net. 5 NS ns01.btsaas.net.
btsaas.net. 5 NS ns04.btsaas.net.
btsaas.net. 5 NS dns1.p05.nsone.net.
btsaas.net. 5 NS dns2.p05.nsone.net.
btsaas.net. 5 NS dns3.p05.nsone.net.
btsaas.net. 5 NS dns4.p05.nsone.net.
btsaas.net. 5 NS ns03.btsaas.net.
btsaas.net. 5 NS ns02.btsaas.net.
Authority
The response has no authority records.
Additional
ns01.btsaas.net. 5 A 45.54.86.1
ns02.btsaas.net. 5 A 45.54.86.65
ns03.btsaas.net. 5 A 45.54.86.129
ns04.btsaas.net. 5 A 45.54.86.193
ns01.btsaas.net. 5 AAAA 2607:f740:e045:0:0:0:0:1
ns02.btsaas.net. 5 AAAA 2607:f740:e045:4:0:0:0:1
ns03.btsaas.net. 5 AAAA 2607:f740:e045:8:0:0:0:1
ns04.btsaas.net. 5 AAAA 2607:f740:e045:c:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0