Don't return AUTHORITY section on a first answers
Compare first query:
$ dig pir.org +dnssec +multi
;; ->>HEADER<<- opcode: QUERY; status: NOERROR; id: 59384
;; Flags: qr rd ra; QUERY: 1; ANSWER: 1; AUTHORITY: 4; ADDITIONAL: 1
;; EDNS PSEUDOSECTION:
;; Version: 0; flags: do; UDP size: 4096 B; ext-rcode: Unused
;; QUESTION SECTION:
;; pir.org. IN A
;; ANSWER SECTION:
pir.org. 300 IN A 97.107.141.235
;; AUTHORITY SECTION:
pir.org. 300 IN NS ns1.ams1.afilias-nst.info.
pir.org. 300 IN NS ns1.mia1.afilias-nst.info.
pir.org. 300 IN NS ns1.sea1.afilias-nst.info.
pir.org. 300 IN NS ns1.yyz1.afilias-nst.info.
;; Received 160 B
;; Time 2017-01-13 13:45:57 CET
;; From ::1@53(UDP) in 626.9 ms
and all next queries answered from cache:
$ dig +dnssec +multi pir.org +dnssec
;; ->>HEADER<<- opcode: QUERY; status: NOERROR; id: 39881
;; Flags: qr rd ra; QUERY: 1; ANSWER: 1; AUTHORITY: 0; ADDITIONAL: 1
;; EDNS PSEUDOSECTION:
;; Version: 0; flags: do; UDP size: 4096 B; ext-rcode: Unused
;; QUESTION SECTION:
;; pir.org. IN A
;; ANSWER SECTION:
pir.org. 287 IN A 97.107.141.235
;; Received 52 B
;; Time 2017-01-13 13:46:10 CET
;; From ::1@53(UDP) in 0.1 ms