Edit in JSFiddle

body {margin: 0;padding:0;}
.box {
    position: relative;
    margin: 20px auto;
    border: 10px solid black;
    width: 150px;
    height: 150px;
    background-color: gold;
}

.radius {
    border-radius: 50px;
}

.outer-border:after {
    content: "";
    position: absolute;
    top: -30px;
    right: -30px;
    bottom: -30px;
    left: -30px;
    border: 10px solid tomato;
}

<div class="box radius outer-border"></div>