Apex domains cannot have CNAME records.
Question and response
Question
dig hosterby.com. NS
Answer
hosterby.com. 5 NS ns1.hosterby.com.
hosterby.com. 5 NS ns2.hosterby.com.
Authority
The response has no authority records.
Additional
ns1.hosterby.com. 5 A 93.125.31.240
ns2.hosterby.com. 5 A 185.179.82.103
ns1.hosterby.com. 5 AAAA 2a0a:7d80:1:1:0:0:5:0
ns2.hosterby.com. 5 AAAA 2a0a:7d80:3:1:0:0:0:7
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0