Assuming this is Web app on Windows plan you should set netFrameworkVersion to value v8.0 and metadata to [{ "name": "CURRENT_STACK", "value": "dotnet"}]. I do not think windowsFxVersion is used in that case and it should be empty string. Note that you mention web app but your code says function app so it is unclear which is it. If it is for function app the same value is for netFrameworkVersion but metadata property is not needed for functions.