<div class="container">
  <div class="inner">
        <img src="https://source.unsplash.com/featured/600x400" alt="#">
  </div>
</div>

.container {
  padding: 20px;
}

img {
  display: block;
  max-width: 100%;
  height: auto;
  border-radius: 36px;
}

.inner {
  max-width: 600px;
  position: relative;
}

.inner::before {
  content: '';
  position: absolute;
  width: 100%;
  height: 100%;
  top: -15px;
  left: -15px;
  border: 3px solid #CC0000;
  border-radius: 36px;
}