Place your large skillet over medium-high heat. Add the ground beef, breaking it apart with a wooden spoon. Listen for that satisfying sizzle. As the meat browns, you are building layers of flavor. Drain the excess fat, leaving just a teaspoon in the pan for the vegetables.

Add the finely diced yellow onion and green bell pepper to the skillet. Sauté them until the onions are translucent and the peppers are tender. Add the garlic in the last minute, stirring constantly so it becomes fragrant without scorching.

Turn the heat down to medium-low. Stir in the ketchup, tomato sauce, brown sugar, yellow mustard, and Worcestershire sauce. Season with salt and black pepper to your liking.

Let the mixture simmer gently for about 10 to 15 minutes. This allows the sauce to thicken and the flavors to marry. If it gets too thick, add a splash of water or beef broth.

While the meat simmers, melt a little butter in another pan. Toast your hamburger buns until they are crisp and golden brown.