JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li style="background-color: aqua;">Dashboard</li>
    <li>Voertuigen</li>
    <li>Klanten</li>
    <li>Factures</li>
    <li>Boetes</li>
    <li>Onderhoud</li>
</ul>

CSS

ul {
    list-style: none;
    -moz-border-radius: 15px;
    -webkit-border-radius: 15px;
    border-radius: 15px;
    width: 140px;
    border: 10px solid #BEBEBE;
}

ul li {
    height: 40px;
    position:relative;
    z-index:-1;
    background: #E5E5E5;
}