JSFiddle - React, Tailwind, and code Playground

HTML

<div class="table">
    <div class="table-row">
        <div class="table-cell-1">
            <a>need 100%!</a>
        </div>
        <div class="table-cell-2">
            some content<br>
            that is <br>
            quite high
        </div>
     </div>
</div>

CSS

.table {
    display:table;
}

.table-row {
    display:table-row;
}

.table-cell-1, .table-cell-2 {
    display:table-cell;
    width:100px;
}

.table-cell-1 {
    background-color:red;
    height: 100px;
}

.table-cell-2 {
    background-color:green;
}

.table-cell-1 a {
    display: inline-table;
    background-color:#ccc;
    height:100%;
    min-height:100%;
}