自建的权威 DNS 服务器能否当查询是 A 记录的时候应答 CNAME 记录？

CNAME 会继承 TXT SOA MX 等记录，从而引起冲突，所以你怎么做都是不规范的

RFC 1034 Domain Concepts and Facilities November 1987

[Page 15]

If a CNAME RR is present at a node, no other data should be present.

[Page 24]

If the data at the node is a CNAME, and QTYPE doesn't match CNAME, copy the CNAME RR into the answer section of the response, change QNAME to the canonical name in the CNAME RR, and go back to step 1.

所以当你 Zone 里对应域名节点是 CNAME 的时候，任何查询都应该返回 CNAME 记录，不论是 A 或者是 AAAA TXT MX 都一样。