Where is this method? Visual Studio keeps bitching that 'UmbracoHelper' does not contain a definition for 'RenderMacroAsync' and no accessible extension method 'RenderMacroAsync' accepting a first argument of type 'UmbracoHelper' could be found (are you missing a using directive or an assembly reference?) What am I missing here? Something that goes in the view imports?

What version of Umbraco are you using?

RenderMacroAsync is a Method on the UmbracoHelper itself in versions below v14. As of v14 Macro support has been removed, as blocks are now supported in the RTE. https://github.com/umbraco/Announcements/issues/14

@Jason Good to know. This one is actually user error. I was trying to render a Macro in a Partial view outside of Umbraco.