Apex domains cannot have CNAME records.
Question and response
Question
dig dsl.sta.mana.pf. NS
Answer
dsl.sta.mana.pf. 5 NS ns1.mana.pf.
dsl.sta.mana.pf. 5 NS ns2.mana.pf.
Authority
The response has no authority records.
Additional
ns1.mana.pf. 5 A 202.3.225.10
ns2.mana.pf. 5 A 202.3.225.20
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0