I want to log the logs of a controller in a new log file

In Symfony 5.4, and by using monolog 3.8. I want to log the request handling of a specifique controller, in a new log file . for my case is citiesController
this my monolog config.

monolog:
    channels:
        - deprecation 
        - cities_controller

when@dev:
    monolog:
        handlers:
            main:
                type: stream
                path: "%kernel.logs_dir%/%kernel.environment%.log"
                level: debug
                channels: ["!event"]
            # uncomment to get logging in your browser
            # you may have to allow bigger header sizes in your Web server configuration
            #firephp:
            #    type: firephp
            #    level: info
            #chromephp:
            #    type: chromephp
            #    level: info
            cities_controller_log:
                type: stream
                path: "%kernel.logs_dir%/CitiesController.log"
                level: debug
                channels: ['cities_controller']
            console:
                type: console
                process_psr_3_messages: false
                channels: ["!event", "!doctrine", "!console"]
           

I expect to get the logs of the cities controller in a new file called citiesController.log
but as far as I check the log file doesn’t get created .
I get the logs in var/dev.logs