JSFiddle - React, Tailwind, and code Playground

HTML

<div class="Amarillo">
    <div class="RojoTransparente">
        <p>Texto. Este no debe de estar transparente</p>
    </div>
</div>

CSS

div.Amarillo {
    height: 150px; width: 400px;
    background-color: rgb(255, 255, 0);
}
div.RojoTransparente {
    height: 50px; position: relative; left: 50px; 
    background-color: rgba(255, 0, 0, 0.2);}
p {background-color: #F00; color: #FFF;}