JSFiddle - React, Tailwind, and code Playground

HTML

<div class="circle">
		<div class="innerCircle"></div>
	</div>

CSS

.circle {
  width: 50px;
  height: 50px;
  background: red;
  position: relative;
  border: 10px solid blue;
}

.innerCircle {
  position: absolute;
  left: 0;
  right: 0;
  top: 0;
  bottom: 0;
  background: black;
  /*border-radius: 100%;*/
}