Apex domains cannot have CNAME records.
Question and response
Question
dig blue.rockhoster.in. NS
Answer
blue.rockhoster.in. 5 NS ns1.44-223-126-41.cprapid.com.
blue.rockhoster.in. 5 NS ns2.44-223-126-41.cprapid.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0