JSFiddle - React, Tailwind, and code Playground

HTML

<div class="q-rounder"><div class="quarter-circle"></div></div>

CSS

.q-rounder{ 

  background: #222; 
  width: 15px; height: 15px;
 }
.quarter-circle{
  width: 15px;
  height: 15px;
  background: red;
  border-radius: 100px 0 0 0;
  -moz-border-radius: 100px 0 0 0;
  -webkit-border-radius: 100px 0 0 0;
}