HTML:

<ya-template-layout ya-key="buttonTemplate">
    <div class='my-button [if state.selected]my-button-selected[endif]'>
        $[data.content]
    </div>
</ya-template-layout>
<ya-map ya-zoom="10" ya-center="[37.62708,55.650625]" ya-controls="">
    <ya-control ya-type="button" ya-params="Жмак-жмак" ya-options="{layout:'buttonTemplate'}"></ya-control>
</ya-map>

CSS

.my-button-selected {
    color: #333333;
    background-color: #e6e6e6;
    outline: 2px dashed #333;
    outline: 5px auto -webkit-focus-ring-color;
    outline-offset: -2px;
}

.my-button {
    display: inline-block;
    padding: 4px 14px;
    margin-bottom: 0;
    font-size: 14px;
    line-height: 20px;
    color: #333333;
    text-align: center;
    vertical-align: middle;
    cursor: pointer;
    background-color: #f5f5f5;
    border: 1px solid #bbbbbb;
    border-color: #e6e6e6 #e6e6e6 #bfbfbf;
    font-family: Arial;
}
    
$[data.content]