UPDATE:- Sitemap on Error Page is now removed in Genesis 3.0+
Step 1
Copy 404.php from Genesis directory into your active child theme directory.
Step 2
Edit the above file and comment out or delete
if ( genesis_a11y( '404-page' ) ) { echo '<h2>' . __( 'Sitemap', 'genesis' ) . '</h2>'; genesis_sitemap( 'h3' ); } else { genesis_sitemap( 'h4' ); }