Note that the .Render method was created before we merged Node and Page and … everything got to be a page. And I kind of forgot about it; the old regular pages works a little bit special in the template/layout department, which .Render hooks into. I will fix that, but not right now.
So, if that is your entire layouts/index.html, it doesn’t make sense as a home page template.
The
{{ .Render "content-single" }}
Is even saying “single”, which is a little misldeading for a Home page. But that will with Hugo 0.20 only render blank, with a WARNING in the log. A partial may be better in this case, not sure.