Otherwise you would have to add a special output format and media type to your config and assign the created output format to the homepage::
# config.yaml
mediaTypes:
text/headers_file:
delimiter: ''
suffixes:
- ''
outputFormats:
headers_file:
baseName: _headers
isPlainText: true
mediatype: text/headers_file
notAlternative: true
outputs:
homepage:
- HTML
- headers_file
Then add a layouts/index.headers_file
to your layouts directory (targeting the homepage and use Go Template in there to generate what you need.