JSFiddle - React, Tailwind, and code Playground

HTML

<div class="active">hi</div>

CSS

.active{
    border:1px solid red;
    border-bottom:0;
    width:80px;
    height:40px;
    margin:30px;
    position:relative;
    -moz-border-radius:5px 5px 0 0;
    -webkit-border-radius:5px 5px 0 0;
}
.active:after,
.active:before{
    content:'';
    width:40px;
    height:30px;
    border:1px solid red;
    position:absolute;
    bottom:-3px;
    border-top:0;
}
.active:after{
    border-left:0;
    -moz-border-radius:0 0 5px 0;
    -webkit-border-radius:0 0 5px 0;
    left:-41px;
}
.active:before{
    border-right:0;
    -moz-border-radius:0 0 0 5px;
    -webkit-border-radius:0 0 0 5px;
    right:-41px;
}