<?php

add_action( 'genesis_before_loop', 'sk_latest_post', 15 );
function sk_latest_post() {
	// WP_Query arguments
	$args = array (
		'cat'            => get_query_var( 'cat' ),
		'no_found_rows'  => true,
		'posts_per_page' => '1',
	);

	// The Query
	$query = new WP_Query( $args );

	// The Loop
	if ( $query->have_posts() ) {
		while ( $query->have_posts() ) {
			$query->the_post();
			// do something
			the_title();
		}
	} else {
		// no posts found
	}

	// Restore original Post Data
	wp_reset_postdata();
}

genesis();