JSFiddle - React, Tailwind, and code Playground

HTML

<div class="triangle-left"></div>
<div class="triangle-left-down"></div>
<div class="bar"></div>

CSS

.triangle-left {
	width: 0;
	height: 0;
	border-top: 100px solid red;
	border-right: 100px solid transparent;

}

.triangle-left-down {
	width: 0;
	height: 0;
	border-bottom: 100px solid red;
	border-right: 100px solid transparent;

}

.bar{
    width:1000px;
    height:200px;
    background-color:red;
    position:absolute;
    margin-left:100px;
    margin-top:-200px;
}