Prepare the aromatics: Mince the garlic, dice the onion, chop the green onion, and dice the tomatoes.
Cook the beef: Heat a bit of oil in a pan over medium heat. Add the ground beef and sauté until browned and slightly crispy, about 5 minutes.
Add the aromatics: Stir in the garlic, diced onion, and the white parts of the green onion. Sauté for about 2 minutes until the onions soften and the mixture becomes fragrant.
Cook down the tomatoes: Add the diced tomatoes and let them cook down, stirring occasionally, until they start to break apart and release their juices. This creates the sweet and tangy backbone of the sauce.
Season the sauce: Pour in the soy sauce, sugar, ketchup, and water. Stir everything together and let it simmer for a few minutes so the flavors can meld.
Thicken the sauce: Slowly drizzle in the cornstarch slurry while stirring to avoid clumps. Allow the mixture to simmer until the sauce reaches your desired thickness, glossy and rich.
Serve and enjoy: For extra comfort, crack an egg directly into the sauce. Cover the pan with a lid and let it cook for about 2 minutes over medium heat until just set. Spoon the tomato beef mixture over a hot bowl of rice. Enjoy!