Can't set log_bin_trust_function_creators=1 on machine startup - MySQL 8.0 I'm trying to put the log_bin_trust_function_creators=1 parameter into the my.cnf configuration file to set the variable correctly on startup on a machine with Ubuntu 20.04 LTS. But every time I save the file with this line written in the config file,  when I try to access the db I can't log in and iIhave this error output message:

mysql: [ERROR] Found option without preceding group in config file /etc/mysql/my.cnf at line 23.
mysql: [ERROR] Fatal error in defaults handling. Program aborted!


When I use SET GLOBAL log_bin_trust_function_creators=1; the parameter and the db work fine, but I would prefer to not having to reboot the machine when I set this parameter.
The version that we're using is mysql  Ver 8.0.20-0ubuntu0.20.04.1 for Linux on x86_64 ((Ubuntu))
Can someone help me with this problem?
Put it under mysqld, there it should be found and set
[mysqld]
log-bin-trust-function-creators = 1