JSFiddle - React, Tailwind, and code Playground

HTML

<div id="main">
    <div id="back">
        <div id="head">
            <div id="title"><h2>Заголовок</h2></div>
        </div>
        <div id="content">
            Содержимое блока
        </div>
    </div>
</div>

CSS

#head{
    height:35px;
    max-width:250px;
}
#title{
    height:34px;
    border:1px solid #A3D869;
    
   
    float:left;
    border-top-left-radius:7px;
    border-top-right-radius:7px;
    background:#C9E39C;
    border-bottom:none;
    box-shadow:0 0 5px #AAA;
}
#title h2{
    font-family:Verdana;
    font-weight:bold;
    background:#C9E39C;
    height:29px;
    padding:5px;
}
#content{
    margin-top:-1px;
    border:1px solid #A3D869;
    padding:15px;
    min-height:100px;
    border-bottom-left-radius:7px;
    border-bottom-right-radius:7px;
    background:#C9E39C;
    z-index:1;
    box-shadow:0 0 5px #AAA;
}