01 - Heat a large skillet over medium-high heat. Add ground beef and cook, breaking apart with a spatula, until browned and no longer pink, about 5 minutes. Drain excess fat if necessary.
02 - Add diced onion, green bell pepper, and minced garlic to the skillet. Cook until vegetables soften, approximately 3 to 4 minutes.
03 - Stir in tomato sauce, tomato paste, ketchup, Worcestershire sauce, brown sugar, yellow mustard, smoked paprika, black pepper, salt, and optional red pepper flakes. Mix thoroughly to blend flavors.
04 - Reduce heat to low and simmer uncovered, stirring occasionally, until sauce thickens, about 10 to 12 minutes. Adjust seasoning to taste.
05 - Optionally, spread butter on the insides of the hamburger buns and toast them in a skillet or under the broiler until golden brown.
06 - Spoon the beef mixture generously onto the bottom half of each toasted bun. Add sliced pickles if desired, then cover with the top bun and serve immediately.