The web server built-in Azure app service

Background:

I am hosting a static web app, generated by NUXTJS on an Azure App Service. Now I'm want to configure something more by the web.config like set CORS setting for multiple domains. But I cannot find any document to figure out what kind of web server has been integrated/installed within the azure app service.

Questions:

1. Maybe an IIS if the platform is Window based, otherwise Apache when creating AAS in Linux based?
2. And what is the corresponding version for each?