Display an object between summary and content in article detail

I am developing a blog layout using the middleman-blog and middleman 4.

In my specific case, in the blog articles page I want to put an object between the summary and the rest of the content, but I did not figure out how to do this because I did not discover how to replace the yield of the template with an option that uses summary + content (excluding the summary text of it)

In this case, I want something like this

<%= article.summary %>
<div class="ad"> ... </div>
<%= current_article.body.sub(current_article.summary, '') %>

But in spite of having arrived at that solution for the case, but I did not know where to apply it, because I did not understand how to replace the yield of the blog template by that code.

This is my article.erb:

<% wrap_layout :layout do %>
  <article>
    <main>
      <%= yield %>
    </main>
  </article>
<% end %>

And here is the excerpt of config.rb:

activate :blog do |blog|
  blog.permalink = "{year}/{month}/{day}/{title}.html"
  blog.sources = "/posts/{year}-{month}-{day}-{title}.html"
  blog.layout = "article"
  blog.summary_separator = /(SEPARADOR)/
  blog.summary_length = 250
end

Thanks for anyone who can help me to clarify the ideas in this regard.

I did a test replacing the yield with the tags and it worked. I felt dumb now. Even so, thanks to anyone who has read it anyway.