Apex domains cannot have CNAME records.
Question and response
Question
dig cust.tele2.ee. NS
Answer
cust.tele2.ee. 5 NS ns.tele2.ee.
cust.tele2.ee. 5 NS ns1.tele2.ee.
Authority
The response has no authority records.
Additional
ns.tele2.ee. 5 A 95.153.47.100
ns1.tele2.ee. 5 A 81.21.241.254
ns.tele2.ee. 5 AAAA 2a01:1b8:0:10:0:0:0:1
ns1.tele2.ee. 5 AAAA 2a01:1b8:ffff:fffe:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0