Magento controller only executing once – cannot disable cache

I have a controller that only executes once after the cache is cleared. After that the response is always the same – cache is there instead of a new execution.

The class is extendsMagentoFrameworkAppActionAction:

class Index extends MagentoFrameworkAppActionAction

What can I do inside this controller to get rid of the cache activity?

This is not related to any block, meaning that it cannot be done via xml cacheable=false option.

Thank you !