Host sets website root to rails 6 public folder... why?

Hello.
My host service sets website root at my rails 6 app public folder.
This results in rendering the static public/index.html instead of root 'pages#index' each time i visit the website url.
If i delete the public/index.html the website hangs with 403 Forbidden message.
Obviously it tries to find an index file inside the public folder and it fails.

How do i fix this?
Is it on the rails level or on apache/nginx/phusion passenger settings?

Plesk Obsidian, Ruby 2.6.3, Rails 6.1.4.1 in production mode.