JSFiddle - React, Tailwind, and code Playground

HTML

<div id="top"></div>
<div id="bottom"></div>

CSS

div {
width:290px; height:10px;   
}

#top {
margin-left:10px; padding-left:-10px;
border-bottom:solid 1px #000;
border-right:solid 1px #000;
border-bottom-right-radius:10px;
}

#bottom {
position:relative; top:-1px;
margin-right:10px; paddding-right:-10px;
border-top:solid #000 1px;
border-left:solid #000 1px;
border-top-left-radius:10px;
}