JSFiddle - React, Tailwind, and code Playground

HTML

<div id="pointed">
    hello
</div>

CSS

#pointed {
position: relative;
margin: 0 auto;
width: 50px;
height: 50px;
padding: 4px;
color: white;
background-color: rgba(0,0,0,.8);
}

#pointed:after,
#pointed::after {
position: absolute;
top: -5px;
left: 22px;
content: '';
width: 0;
height: 0;
border-bottom: solid 5px rgba(0,0,0,.8);
border-left: solid 5px transparent;
border-right: solid 5px transparent;
}