Redirect a subsite in an Azure web app to a different site

An Azure web app has several subsites/virtual paths:

• azure-web-app.com/subsite1

• azure-web-app.com/subsite2

• azure-web-app.com/subsite3

Is it possible to configure the site such that when azure-web-app.com/subsite3 is accessed by the user in the browser, it automatically redirects to completely-different-site.com?

I have not tested potential solutions I have read about because there is only a prod instance of the site (no dev - I know that is not a best practice) and it would be helpful to know where to head before proceeding.

Other info:

• The site has a custom domain applied - e.g., azure-web-app.com.
• Stack is .NET v4.7

I can provide any missing details. Thanks for any help.