Apex domains cannot have CNAME records.
Question and response
Question
dig thisalabs.com. NS
Answer
thisalabs.com. 2 NS ns2.thisalabs.com.
thisalabs.com. 2 NS ns1.thisalabs.com.
Authority
The response has no authority records.
Additional
ns1.thisalabs.com. 2 A 217.13.101.212
ns2.thisalabs.com. 2 A 217.13.101.237
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0