Function to call in a custom 404 template for Genesis WordPress.

Custom_404_function.php

remove_action( 'genesis_loop', 'genesis_404' ); // Remove the default Genesis 404 content
add_action( 'genesis_loop', 'cd_custom_404' ); // Add function for custom 404 content

function cd_custom_404() {

    if ( is_404() ) {
        get_template_part('/partials/sitemap'); // Plop in our customized sitemap code
    }

}