Preheat oven to 350 degrees F (175 degrees C). Lightly grease a 9x5-inch loaf pan.
Stir ketchup, brown sugar, salt, and chili powder together in a bowl until smooth. Spread a small amount of the ketchup mixture into the bottom of the prepared loaf pan.
Mix ground beef, croutons, onion, eggs, milk, and black pepper together in a large bowl; shape into a loaf and put into prepared pan. Spread remaining ketchup mixture over the loaf.
Bake in the preheated oven until no longer pink in the center, about 1 hour. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C).
