Apex domains cannot have CNAME records.
Question and response
Question
dig cpt2.host-h.net. NS
Answer
cpt2.host-h.net. 3 NS ns2.host-h.net.
cpt2.host-h.net. 3 NS ns1.dns-h.com.
cpt2.host-h.net. 3 NS ns1.host-h.net.
cpt2.host-h.net. 3 NS ns2.dns-h.com.
Authority
The response has no authority records.
Additional
ns1.dns-h.com. 2 A 129.232.248.31
ns1.host-h.net. 2 A 129.232.248.30
ns2.dns-h.com. 2 A 129.232.248.41
ns2.host-h.net. 2 A 129.232.248.40
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0