JSFiddle - React, Tailwind, and code Playground

HTML

<div class = "my_block">
</div>

CSS

body{
  background-color: #fff;
}
.my_block{
  width: 300px;
  height: 90px;
  background-color: #000;
  position: relative;
}
.my_block:after{
  display: block;
  position: absolute;
  content: '';
  top: 0px;
  right: -35px;
  border-top: 45px solid #000;
  border-right: 35px solid transparent;
  border-bottom: 45px solid #000;
}