In a large bowl, put the hamburger, bread, eggs, onion, tomato sauce, salt and pepper. Using your hands, mix everything together. Continue mixing until all of the ingredients are evenly distributed. Take your time, and do it well. Press this mixture into a 9- by 5-inch loaf pan, or another 2-quart size pan (like a casserole). Pack it tightly and smooth it so it looks nice on top.Bake at 350F for at least an hour. If the meat was cold from the fridge, bake for 1 1/2 hours. Remove the meatloaf from the oven. Let it rest for a few minutes to firm up. Drain off the fat if desired.