Apex domains cannot have CNAME records.
Question and response
Question
dig serverastra.com. NS
Answer
serverastra.com. 1 NS dns1.serverastra.com.
serverastra.com. 1 NS dns2.serverastra.com.
Authority
The response has no authority records.
Additional
dns1.serverastra.com. 1 A 91.219.236.24
dns2.serverastra.com. 1 A 51.38.70.163
dns1.serverastra.com. 1 AAAA 2a10:c800:0:0:0:0:0:24
dns2.serverastra.com. 1 AAAA 2001:41d0:801:2000:0:0:0:1269
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0