<div class="out">
<div class="in"></div>
</div>
<style>
*{background: #F3EAD2}
body {
display: flex;
justify-content: center;
align-items: center;
height: 100%;
margin: 0;
}
.out {
border: 2.5rem solid #EAC049;
height: 7.5rem; width: 7.5rem;
}
.in {
height: 0;
width: 0;
border: 3.75rem solid;
border-color: #F3EAD2 #EAC049 #EAC049 #F3EAD2;
}
</style>