Apex domains cannot have CNAME records.
Question and response
Question
dig sol-bd.com. NS
Answer
sol-bd.com. 5 NS nameserver1.sol-bd.com.
sol-bd.com. 5 NS nameserver2.sol-bd.com.
Authority
The response has no authority records.
Additional
nameserver1.sol-bd.com. 5 A 103.49.200.2
nameserver2.sol-bd.com. 5 A 103.49.200.7
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0