Even though you changed error.log to something else in logspec.xml, CQ still writes both in error.log and the new log file.

Solution

Under server/runtime/0/_author/WEB-INF/web.xml locate the cq.logfile parameter, and replace the param-value by your own custom log file. For example:

${cq.home}/logs/cmserror.log

Additional information

Until the logspec.xml is parsed during the Communiqué startup, the default behavior is to log the entries in logs/error.log.