JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

div {
  height: 100px;
  width: 100px;
  
  background: linear-gradient(120deg, transparent 63%, white 63%),
              linear-gradient(-120deg, transparent 63%, white 63%),
              linear-gradient(to top, blue, blue);
}