01 - Heat a large skillet over medium-high heat. Add the ground beef and cook, breaking up the meat with a spatula, until browned and no longer pink, about 5 minutes. Drain excess fat if needed.
02 - Add the chopped onion, bell pepper, and garlic to the skillet with the beef. Sauté for 3–4 minutes until the vegetables are softened and fragrant.
03 - Stir in the tomato sauce, tomato paste, ketchup, Worcestershire sauce, brown sugar, yellow mustard, smoked paprika, salt, black pepper, and red pepper flakes if using. Mix thoroughly to combine all ingredients.
04 - Reduce heat to low and let the mixture simmer uncovered for 8–10 minutes, stirring occasionally, until the sauce has thickened to a hearty consistency.
05 - While the mixture simmers, butter the cut sides of the hamburger buns if desired. Toast them on a skillet or griddle until golden and lightly crisp.
06 - Spoon the Sloppy Joe mixture generously onto the bottom half of each toasted bun. Top with the remaining bun half and serve immediately while hot.