How to set the seo title tag on a page by page basis?

I added this to functions.php while having Yoast SEO activated, and then it worked!

add_filter('wpseo_title', 'filter_product_wpseo_title');
function filter_product_wpseo_title($title) {
    if(  is_singular( 'my_post_type') ) {   
        $title = get_field("title_tag");
    }
    return $title;
}