Pre-heat the air fryer to 350ºF.

Toss the peppers with a little olive oil and season with salt and freshly ground black pepper. Transfer the peppers to the air fryer basket and air-fry at 350º for 6 minutes, shaking the basket several times during the cooking process.

Brown the ground beef and onions in a large sauté pan over medium-high heat on the stovetop. Drain away the grease and add the garlic, tomato sauce, and Italian seasoning. Cook for 2 minutes. Add the rice, Parmesan cheese and chopped fresh parsley. Season to taste with salt and freshly ground black pepper. Set aside to cool slightly.

When the peppers are soft, remove them from the air fryer and let them cool for a few minutes. Make a slit lengthwise through one side of the pepper, being careful not to cut entirely through the pepper.

Stuff each pepper with the meat mixture. Stuff enough filling inside so that the filling is exposed and the pepper does not shut completely. Top with some mozzarella cheese to cover the meat filling.

Air-fry the peppers in two batches at 370°F for 3 to 4 minutes, until the peppers and filling are heated through and the cheese is melted. Garnish with fresh chopped parsley and serve.