JSFiddle - React, Tailwind, and code Playground

HTML

<div class="box"></div>

CSS

.box {
  width: 250px;
  height: 250px;
  position: relative;
  margin: 30px;
  border-radius: 50%;
  background: #fff;
}
.box:after {
  content: '';
  position: absolute;
  top: -15px;
  bottom: -15px;
  right: -15px;
  left: -15px;
  background-image: linear-gradient(to bottom left, red 30%, yellow 0);
  z-index: -1;
  border-radius: inherit;
}