In a large skillet over medium heat, add a drizzle of oil and toss in your diced onion and bell pepper. Sauté for about 3-4 minutes until they're tender and fragrant.

Add the ground beef to the skillet. Break it apart with a spatula and cook until browned, about 5-7 minutes. Drain any excess fat.

Once the meat is browned, add ketchup, mustard, Worcestershire sauce, brown sugar, salt, and pepper. Stir everything together and let it simmer on low heat for about 5-10 minutes.

Slice your buns and toast them in the oven or on a skillet.

Spoon the meat mixture onto the bottom half of each bun, add your desired toppings, and crown it with the top half.