SOURCE

<div class="box">
    <div class="block"></div>
</div>

.block {
    width: 200px;
    height: 200px;
    background-image: radial-gradient(circle 200px at 50% 0, transparent 30px, #000 30px);
    margin: 300px;
    border-radius: 20px;
}

.box{
    filter:drop-shadow(0 2px 3px #fff);
}