Apex domains cannot have CNAME records.
Question and response
Question
dig avala.bg. NS
Answer
avala.bg. 5 NS lada.avala.bg.
avala.bg. 5 NS volos.avala.bg.
Authority
The response has no authority records.
Additional
lada.avala.bg. 5 A 185.253.159.2
volos.avala.bg. 5 A 185.253.159.3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0