JSFiddle - React, Tailwind, and code Playground

HTML

<div class="content__header">
  <div class="content__corner"></div>
</div>

SCSS

.content {
  &__header {
    background-color: #fff;
    position: relative;
    height: 60px;
    width: 100%;
    padding: 0;
  }

  &__corner {
    float: left;
    height: 60px;
    overflow: hidden;
    position: relative;
    width: 100%;

    &::after {
      border-bottom: 60px solid #a4a4a4;
      border-right: 90vw solid transparent;
      content: '';
      height:0;
      position: absolute;
      width:0;
    }
  }
}