JSFiddle - React, Tailwind, and code Playground

HTML

<div class="a">
    <div id="b"></div>
</div>

CSS

body {
    width:100%;
    margin:0;
    background: #000;
}
#b {
    position:relative;
    width:500px;
    height:90px;
    margin: 100px auto;
    font-size: 12px;
}
#b:before {
    position: absolute;
    content:"";
    left: 208px;
    top: 10px;
    width: 208px;
    height: 320px;
    background: red;
    border-radius: 200px 200px 0 0;
    box-shadow: 0 0 50px #fff;
}
#b:before {
    -webkit-transform: rotate(-45deg);
    -moz-transform: rotate(-45deg);
    -ms-transform: rotate(-45deg);
    -o-transform: rotate(-45deg);
    transform: rotate(-45deg);
    -webkit-transform-origin: 0 100%;
    -moz-transform-origin: 0 100%;
    -ms-transform-origin: 0 100%;
    -o-transform-origin: 0 100%;
    transform-origin: 0 100%;
}
#b:after {
    position:absolute;
    content:"BlaBla!";
    color: #fff;
    left:0;
    top:10px;
    width:208px;
    height:320px;
    background: red;
    border-radius:200px 200px 0 0;
    -webkit-transform:rotate(45deg);
    -moz-transform:rotate(45deg);
    -ms-transform:rotate(45deg);
    -o-transform:rotate(45deg);
    transform:rotate(45deg);
    -webkit-transform-origin:100% 100%;
    -moz-transform-origin:100% 100%;
    -ms-transform-origin:100% 100%;
    -o-transform-origin:100% 100%;
    transform-origin:100% 100%;
    box-shadow: 10px 10px 100px #6d0019;
}