01 - Heat a large skillet over medium heat. Add the ground beef and cook, breaking it up with a spatula, until browned and no longer pink, about 5 minutes. Drain excess fat if necessary.
02 - Add the chopped onion, green bell pepper, and minced garlic to the skillet. Cook for 3–4 minutes, until softened and fragrant.
03 - Stir in the tomato sauce, ketchup, tomato paste, Worcestershire sauce, brown sugar, mustard, smoked paprika, chili powder, salt, and black pepper. Mix well to combine all ingredients.
04 - Reduce heat to low and simmer the mixture, uncovered, for 10–12 minutes, stirring occasionally, until thickened to your desired consistency.
05 - While the filling simmers, optionally butter the cut sides of the buns and toast them in a skillet or under the broiler until golden brown.
06 - Spoon generous portions of the beef mixture onto the bottom halves of the buns. Top with the other halves and serve immediately.