-3
You need to adjust the border-radius of its element, if it is large enough the element will be round:
img {
  background-color: blue;
  width: 200px;
  height: 200px;
}
.capa {
    width: 210px;
    height: 210px;
}
.cd {
  position: absolute;
  z-index: -1;
  border-radius: 100px;
  border: 2px solid gray;
  left: 100px;
}<img class="capa" src="https://upload.wikimedia.org/wikipedia/commons/a/af/Tux.png">
<img class="cd" src="https://upload.wikimedia.org/wikipedia/commons/a/af/Tux.png">

That’s not an effect, it’s an image... Or is that what you want is, given a "normal" image, create underneath a round element with the same image to look like a CD?
– mgibsonbr