Apex domains cannot have CNAME records.
Question and response
Question
dig 3dg.se. NS
Answer
3dg.se. 5 NS ns1.3dg.se.
3dg.se. 5 NS ns2.3dg.se.
3dg.se. 5 NS ns3.3dg.se.
3dg.se. 5 NS ns4.3dg.se.
Authority
The response has no authority records.
Additional
ns1.3dg.se. 5 A 82.99.18.107
ns2.3dg.se. 5 A 94.246.96.110
ns3.3dg.se. 5 A 62.109.34.73
ns4.3dg.se. 5 A 94.130.116.49
ns1.3dg.se. 5 AAAA 2a01:2b0:301d:99:0:0:0:107
ns2.3dg.se. 5 AAAA 2a01:2b0:301d:88:0:0:0:110
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0