<div id="css-sawtooth-bg"><div id="css-sawtooth-actual"></div></div>

#css-sawtooth-bg {
    background: radial-gradient(circle, #ac1d1c, #eca);
    height: 100px;
    display: flex;
    align-items: center;
    justify-content: center;
}
#css-sawtooth-actual {
    height: 60px;
    width: 60px;
    background: linear-gradient(to bottom right, white, white 50%, transparent 50%, transparent);
}