Jessica Andrade shocked the world at UFC 237 in Rio de Janeiro, Brazil, when she knocked Rose Namajunas out with a slam in the second round. This slam earned her the UFC women’s strawweight title.
At this point Rose was controlling the fight but Jessica was gaining momentum and I believe that once it was established that Namajunas could not (visibly) hurt Andrade on the feet, eventually the latter would start dominating the fight with her relentless pressure. Rose was already starting to get tired when the slam happened.
As you can see in the tweet above, Rose held onto a kimura grip during the slam and since then there has been a lot of debate about whether the slam was legal or not.