JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div class='active-menu'>
    </div>
</body>

CSS

body {
    background-color: #9E9290;
}

.active-menu {
    background-color:white;
    width: 200px;
    height: 200px;
    border-radius: 15px;
    margin-top: 30px;
}
.active-menu:before{
  content:'';
  position:absolute;
  width:20px;
  height:20px;
  left:160px;
  top:20px;
  transform:rotate(145deg) skew(20deg);
  background:inherit;
}