JSFiddle - React, Tailwind, and code Playground

HTML

<fieldset>
    <legend>My Title</legend>
    <div>
        some content
    </div>
</fieldset>

CSS

legend {
    display: block;
    border-bottom: 1px solid red;
    /*width: 100%;*/
    margin-bottom: 30px;
}
fieldset {
    display: block;
    background: pink;
}
div {
    background: lime;
}