Returning string with diacritics

Question

I want to use FW/1 to return a string that looks like this:

"Wüf!"

framework.renderData().data("Wüf!").type( "text" );

Note that this is not normal FW/1, but REST

When I run this I get

Wüf!

Postman reports in the headers, Content-Type is

text/plain;charset=utf-8

Update

Visual Code Studio reports that the file is UTF-8

Also EncodeForXML() turns it into

Wüf!

Which is worse

Update 2

I tried

<cfprocessingdirective pageencoding="utf-8">
<cfscript>
component   accessors="true" output="false" extends="concerns.rest" {

    property    beanFactory;
    property    framework;

But I get