multidomain long load time to first byte

I am investigating load time of ignisoffice.com with https://www.webpagetest.org.
I have notices that that there is a long, 1 second, time to first byte with something that comes from Multi-domains plugin:
https://budikom.net/dm-sso-endpoint/1474997531/?dm_action=domainmap-setup-cdsso
budikom.net is primary site of this multisite WP installation, where ignisoffice is secondary site.