JSFiddle - React, Tailwind, and code Playground

HTML

<select class="squarecorners">
    <option>Option 1</option>
    <option>Option 2</option>
    <option>Option 3</option>
</select>

CSS

select.squarecorners{
     border: 0;
     outline: 1px solid #CCC;
     background-color: red;
     height: 2em;
     width: 10em;
     font-size: 1em;
}