JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div class="item">
        <div class="item-inner">
            <a>
                Botón
            </a>
        </div>
    </div>
    
    <div class="item">
        <div class="item-inner">
            <a>
                Botón
            </a>
        </div>
    </div>
    
    <div class="item">
        <div class="item-inner">
            <a>
                Botón
            </a>
        </div>
    </div>
</div>

CSS

.container {
    display: flex;
    flex-direction: column;
    height: 20em;
    border: 5px solid black
}

.item {
    display: flex; /* new; nested flexbox */
    flex: 1;
    border-bottom: 1px solid white;
}

.item-inner {
    display: flex; /* new; nested flexbox */
    flex: 1; /* new */
 
    /* height: 100%; <-- remove; unnecessary */
    /* width: 100%; <-- remove; unnecessary */
    /* display: table; <-- remove; unnecessary */  
}

a {
    display: flex; /* new; nested flexbox */
    flex: 1; /* new */
    align-items: center; /* new; vertically center text */
    background: orange;
    
 
    /* display: table-cell; <-- remove; unnecessary */
    /* vertical-align: middle; <-- remove; unnecessary */
    
}