Apex domains cannot have CNAME records.
Question and response
Question
dig nkn.in. NS
Answer
nkn.in. 2 NS ns6.nkn.in.
nkn.in. 2 NS ns1.nkn.in.
nkn.in. 2 NS ns2.nkn.in.
nkn.in. 2 NS ns3.nkn.in.
Authority
The response has no authority records.
Additional
ns1.nkn.in. 2 A 180.149.63.3
ns2.nkn.in. 2 A 180.149.63.66
ns3.nkn.in. 2 A 180.149.63.250
ns6.nkn.in. 2 A 14.139.6.10
ns1.nkn.in. 2 AAAA 2405:8a00:aa:0:0:0:0:aa
ns2.nkn.in. 2 AAAA 2405:8a00:bb:0:0:0:0:bb
ns6.nkn.in. 2 AAAA 2405:8a00:4:0:0:0:0:4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0