500.21 Bad module "ManagedPipelineHandler" in its module list

I ran into this error on a fresh build of Windows Server 2012 R2. IIS and .NET 4.5 had been installed, but the ASP.NET Server Role (version 4.5 in my case) had not been added. Make sure that the version of ASP.NET you need has been added/installed like ASP.NET 4.5 is in this screenshot.

Please follow these steps:

1) Run the command prompt as administrator.

2) Type either of the two lines below in the command prompt:

%windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_regiis.exe -i

or

%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe -i