JSFiddle - React, Tailwind, and code Playground

HTML

<h1>Вот это поворот!</h1>

CSS

h1 {
    font-size: 3em;
    text-align: center;
    padding: 5% 0 1em;
    background: #ccc;
    position: relative;
    overflow: hidden;
}

h1::before {
    content: '';
    display: block;
    width: 72%;
    padding: 72% 0 0;
    margin: auto;
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    background: #fff;
    -webkit-transform: translateY(-50%) scaleY(.1) rotate(45deg);
    transform: translateY(-50%) scaleY(.1) rotate(45deg);
    border-radius: 0 0 50% 0;
}