JSFiddle - React, Tailwind, and code Playground

HTML

<div>
        <div class="button-container" id="but-cont-1">
            <button id="but1">
            </button>       
        </div>
    </div>

CSS

*{
  margin: 0;
  padding: 0;
}

body{
padding: 20px
}
#but1 {
  /* margin-right: 5px; */
  /* background-color: transparent; */
  border: 0;
  background-color: #fff;
  width: 50%;
  height: 50px;
  border-radius: 125px;
  border: 1px solid lightgray;
  box-shadow: 0px 0px 10px 0px rgba(0, 0, 0, 0.2);
}

#but1:before {
  content: "";
  display: block;
  background: url("https://cdn-icons-png.flaticon.com/128/1078/1078599.png") no-repeat;
  background-size: 50%;
  background-position: center right;
  height: 50px;
  width: 50px;
  margin-right: 16px;
  margin-left: auto;
}