Apex domains cannot have CNAME records.
Question and response
Question
dig sme.telenor.se. NS
Answer
sme.telenor.se. 5 NS dns3.telenor.se.
sme.telenor.se. 5 NS ns1.se.telenor.net.
sme.telenor.se. 5 NS ns2.se.telenor.net.
Authority
The response has no authority records.
Additional
ns1.se.telenor.net. 5 A 195.54.122.193
ns2.se.telenor.net. 5 A 195.54.122.194
dns3.telenor.se. 5 A 62.127.3.139
dns3.telenor.se. 5 AAAA 2a02:1400:17:103:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0