Apex domains cannot have CNAME records.
Question and response
Question
dig online.no. NS
Answer
online.no. 5 NS ns1.nextra.no.
online.no. 5 NS ns2.nextra.no.
Authority
The response has no authority records.
Additional
ns1.nextra.no. 5 A 148.122.208.98
ns2.nextra.no. 5 A 148.122.161.2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0