Preheat your air fryer to 375°F (190°C).

Place the ground beef into the air fryer basket, and cook the lean ground beef until it's browned and crumbled. Drain any excess fat.

Add the finely chopped onion, green bell pepper, and minced garlic to the cooked beef.

In a small bowl, whisk together the ketchup, tomato sauce, brown sugar, Worcestershire sauce, mustard, chili powder, salt, and pepper. Pour this sauce mixture over the cooked beef and vegetables in a large bowl.

Return the ground beef mixture to the air fryer and cook for 5-10 minutes at 330 degrees F, stirring occasionally, until the sauce thickens and coats the meat and vegetables.

While the Sloppy Joe mixture is simmering, place the hamburger buns in the air fryer basket or on the air fryer tray. Toast them for 1-2 minutes until lightly golden and crispy.

Spoon a generous portion of the Sloppy Joe mixture onto the bottom half of each toasted bun. Top with the other half of the bun.