1. Preheat your air fryer to 400°F. This ensures a perfect start for cooking.

2. Cook the beef: In a pan, cook 1 lb of lean ground beef over medium heat, breaking it apart until browned, about 5 minutes. Ensure no pink remains.

3. Add veggies: Stir in 1 chopped medium onion and 1 chopped green bell pepper, cooking until they soften, roughly 3 minutes.

4. Mix in the sauce: Add 1 cup ketchup, 2 tablespoons brown sugar, 1 tablespoon Worcestershire sauce, and 1 teaspoon mustard. Season with salt and pepper. Let it simmer for 5 minutes, allowing the flavors to meld.

5. Transfer to the air fryer: Place the beef mixture in an air fryer-safe dish, spreading it evenly.

6. Air fry: Cook the mixture at 400°F for 10 minutes. This step intensifies the sauce’s flavor and texture.

7. Toast the buns: Briefly toast the hamburger buns until lightly golden for a crunch.

8. Assemble: Spoon the mixture onto the buns, cap them off, and press slightly.