Apex domains cannot have CNAME records.
Question and response
Question
dig szerverplex.com. NS
Answer
szerverplex.com. 2 NS dns3.szerverplex.com.
szerverplex.com. 2 NS dns2.szerverplex.com.
szerverplex.com. 2 NS dns1.szerverplex.com.
szerverplex.com. 2 NS dns4.szerverplex.com.
Authority
The response has no authority records.
Additional
dns1.szerverplex.com. 2 A 87.229.77.7
dns2.szerverplex.com. 2 A 79.172.210.7
dns3.szerverplex.com. 2 A 135.125.190.43
dns4.szerverplex.com. 2 A 158.69.205.35
dns1.szerverplex.com. 2 AAAA 2a02:c647:0:1:0:0:0:1
dns2.szerverplex.com. 2 AAAA 2a02:c647:0:2:0:0:0:1
dns3.szerverplex.com. 2 AAAA 2001:41d0:701:1100:0:0:0:47b8
dns4.szerverplex.com. 2 AAAA 2607:5300:201:3000:0:0:0:4296
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0