JSFiddle - React, Tailwind, and code Playground

HTML

<div class="tab">
    <div class="arrow"></div>
</div>

CSS

body {
    background-color: #666;
}
.tab:before {
    height: 50px;
    width: 10px;
    display: block;
    content:" ";
    background-color: #FFF;
    position: absolute;
    right: -2px;
    top: -2px;
    border-top: 2px solid blue;
    border-bottom: 2px solid blue;
}
.tab {
    height: 50px;
    width: 150px;
    border-radius: 10px 10px 0px 0px;
    background-color: #FFF;
    position: relative;
    border: 2px solid blue;
}
.tab:after {
    display: block;
    content:" ";
    width: 100px;
    height: 50px;
    top: -2px;
    background-color: #FFF;
    position: absolute;
    right: -29px;
    transform:skewX(45deg);
    -ms-transform:skewX(45deg);
    -webkit-transform:skewX(45deg);
    border: 2px solid blue;
    z-index: -1;
}