<div></div>

div {
  width: 40px;
  height: 40px;
  border-radius: 100%;
  border: 5px solid red;
  background: red;
  background-clip: content-box;
  padding: 5px;
  box-sizing: border-box;
}

body {
  margin: 0;
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(45deg, red, orange, yellow, green, blue, magenta);
}