Begin by assembling all necessary ingredients. Preheat your oven to 350 degrees Fahrenheit (175 degrees Celsius).

In a small mixing bowl, combine the ketchup, brown sugar, 1 tablespoon of lemon juice, and dry mustard. Stir until the mixture is smooth.

In a large bowl, combine the lean ground beef, shredded bread, 1/3 cup of the ketchup mixture, diced onion, the beaten egg, the remaining 3 tablespoons of lemon juice, and the crumbled bouillon cube. Mix thoroughly until all ingredients are well integrated.

Shape the mixture into a loaf and place it into a 9x5-inch loaf pan.

Bake the meatloaf in the preheated oven for 1 hour. After this time, carefully remove the pan from the oven and drain any excess fat.

Spread the remaining ketchup mixture over the top of the meatloaf. Return it to the oven and continue baking until the meatloaf is no longer pink in the center, which should take about 10 additional minutes. An instant-read thermometer inserted into the center of the loaf should indicate a minimum internal temperature of 160 degrees Fahrenheit (71 degrees Celsius).

Serve the meatloaf hot and enjoy this classic dish!