Use HTTPS URLs in {{{absoluteURL}}}

Hi! I'm having an issue where my Open Graph meta tags are causing problems with link previews on Slack (and others) due to a protocol mismatch?

Currently, my {{{absoluteURL}}} template variable is generating HTTP URLs (like http://mysite.com/blog/post), but my images are served over HTTPS. I think this is preventing Slack from displaying link previews, though they work fine on other platforms like iOS Messages. Not sure why.

Is there a way to configure my blog so that {{{absoluteURL}}} outputs HTTPS URLs instead of HTTP? I've looked through the settings but can't find a site URL or domain configuration option.

My site is accessible via HTTPS, so I'd like the template variables to reflect that.

Thanks!