JSFiddle - React, Tailwind, and code Playground

HTML

<div style="border: 1px solid #000; width:100px; height:100px;">
    <div id="hr" style="border-top:1px solid #ff00ff; height:100px; margin-left:-140px;">   </div>
</div>

CSS

#hr {
     -moz-transform: rotate(45deg);  
       -o-transform: rotate(45deg);  
  -webkit-transform: rotate(45deg);  
      -ms-transform: rotate(45deg);  
          transform: rotate(45deg); 
}