Pro Tips: The #1 secret to a moist meatloaf is to DO NOT OVERMIX – mix ingredients just until combined. Use 80% or 85% lean ground beef for the best flavor and moisture. Sauté the onions to soften their flavor and ensure a better texture. Baking free-form on a sheet pan creates delicious crispy edges. Let the meatloaf rest for 10-15 minutes before slicing to allow juices to redistribute. For the most accurate doneness, use an instant-read thermometer; it should reach 160°F for beef.