Heat oven to 400 degrees. In a bowl, combine beef, bread crumbs, onion, and salt. Gently press mixture into a 8 x 8-inch pan so that it makes one large patty of even thickness. Using a fork, poke holes throughout the meat so the meat will cook evenly. Bake for 20 minutes. As it bakes, the meat will shrink away from the sides and liquid will accumulate around the edges of pan. When fully cooked, remove the pan from oven (keep oven turned on) and carefully drain off the liquid.