JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<div class="bar"></div>

CSS

.bar {
	height: 100px;
	width: 300px;
    background: #BC5859;
    display:inline-block;
    position: relative
}

.bar:before {
    display:inline-block;
    position: absolute;
    content:"";
	border-left: 100px solid #BC5859;
	border-bottom: 100px solid transparent;
	height: 0;
	width: 0px;
    right: -100px;
    top:0;
}