Recent Posts on blog with many authors. ( one per author )

I want to display the loop for the 12 most recent posts on a blog. The blog has many authors, so I just want it to show 1 post per author in this list of 12. So if an author does 6 posts in a row, only the most recent post is shown in the list. How do I achieve that.

This is what I’m using

<ul>
<?php $recent = new WP_Query("showposts=12");
while($recent->have_posts()) : $recent->the_post(); ?>
<li>
<?php echo get_avatar( $post->post_author, 50 ); ?>

<h2><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></a></h2>

</li>

<?php endwhile ; ?>
</ul>

I’m looking at https://codex.www.ads-software.com/Template_Tags/query_posts but I dont see a way to achieve it. I’ve searched but didn’t find any plugins that do this. But I’m sure I just have to manipulate the loop to do it. I just dont know how.