Apex domains cannot have CNAME records.
Question and response
Question
dig i.bitbit.net. NS
Answer
i.bitbit.net. 1 NS ns-foo.i.bitbit.net.
i.bitbit.net. 1 NS ns-bar.i.bitbit.net.
i.bitbit.net. 1 NS ns-zoo.i.bitbit.net.
Authority
The response has no authority records.
Additional
ns-bar.i.bitbit.net. 1 A 87.238.39.51
ns-foo.i.bitbit.net. 1 A 87.238.32.254
ns-zoo.i.bitbit.net. 1 A 69.164.207.59
ns-bar.i.bitbit.net. 1 AAAA 2a02:c0:400:102:0:0:0:b
ns-foo.i.bitbit.net. 1 AAAA 2a02:c0:1001:1:0:0:0:2
ns-zoo.i.bitbit.net. 1 AAAA 2600:3c00:0:0:f03c:91ff:febd:d3ff
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0