Start by warming your air fryer at 400°F for 3 to 5 minutes, adjusting time based on its size.
Meanwhile, slice the tops off the bell peppers, remove seeds, and chop the tops to save for later.
Put the peppers inside the air fryer basket and let them cook for 6 minutes to soften slightly.
Heat olive oil in a deep skillet over medium-high heat, then sauté the diced onion and chopped pepper tops for 2 to 3 minutes until they become translucent.
Add the minced garlic and cook for about 1 to 2 minutes until you smell its aroma.
Introduce the ground beef to the skillet and cook, stirring, until fully browned with no pink remaining, reaching 160°F internally.
Mix in Italian seasoning, salt, diced tomatoes with juices, and coconut aminos or Worcestershire sauce, stirring well.
Add uncooked rice and water, reduce heat to medium-low, cover, and let it simmer for approximately 15 minutes or until rice is tender.
Fill each partially cooked pepper evenly with the beef and rice mixture, then return to the air fryer.
Cook the stuffed peppers at 400°F for 4 minutes, then carefully open the air fryer and sprinkle cheese on top if using.
Continue cooking for another 4 minutes until the cheese melts and bubbles; if skipping cheese, air fry them for an 8-minute stretch.
Once done, let the peppers cool slightly before serving or storing.