1 pound ground beef
1/2 yellow onion, diced
1 clove garlic, minced
1 cup green bell pepper, diced
1 cup celery, chopped thin
3/4 cup ketchup
1 tablespoon Worcestershire sauce
2 tablespoons brown sugar
2 teaspoons mustard
3/4 teaspoon salt
1/4 teaspoon black pepper
1 pinch cayenne pepper

Place ground beef and onion in a large skillet. Turn heat to medium and cook and stir the mixture constantly until the beef is browned and forms small crumbles, about 10 minutes.

Stir in garlic, celery, and green bell pepper; cook and stir until softened, 2 to 3 minutes.

Mix in ketchup, Worcestershire sauce, brown sugar, mustard, salt, and black pepper. Add 1 cup water and return mixture to a simmer.  Reduce heat to low and simmer, stirring occasionally, until the liquid has evaporated and the mixture is thick, about 25-30 minutes.

Season with salt, black pepper, and cayenne pepper to taste. Spoon over warm buns and serve. Mixture should be thick enough to eat like a hamburger.