Ingredients

• 2 tablespoons unsalted butter
• 1 medium onion, diced 
• 1 green bell pepper, diced 
• 1 clove garlic, minced 
• 1 pound lean ground beef 
• 12 ounces (1 1/3 cup) tomato sauce  
• 3/4 cup ketchup 
• 2 tablespoons brown sugar 
• 2 tablespoons Worcestershire sauce 
• 1 tablespoon yellow mustard 
• 1 tablespoon red wine vinegar 
• 1 teaspoon paprika 
• Pinch of cayenne pepper 
• Kosher salt and freshly ground black pepper 
• 6 hamburger buns, toasted 

Instructions

1. Melt the butter in a large skillet over medium-high heat. Add the onions and peppers and cook, stirring occasionally, until softened and starting to caramelize in some spots, 6 to 7 minutes. Add the garlic and cook, stirring, until fragrant, about 1 minute. Stir in the beef and cook, breaking up the meat with a wooden spoon or spatula, until it is browned, no longer pink in the middle and cooked through, 7 to 8 minutes.
2. Stir in the tomato sauce, ketchup, brown sugar, Worcestershire sauce, mustard, red wine vinegar, paprika, cayenne pepper, 1 teaspoon salt and a generous amount of black pepper and simmer, stirring occasionally, until thickened and heated through, 5 to 6 minutes. Spoon the meat onto the toasted buns.