Preheat the air fryer to 360 degrees F or 180 degrees C.
Brown beef in a skillet stirring occasionally, drain any grease and then add in seasoning.
Add red onion, diced tomatoes, and kale and stir fry for 4-6 minutes until veggies are soft.
Stuff the peppers with the ground beef mixture.
Place peppers in the air fryer basket and air fry for 10 minutes.
Top with shredded cheese and cook for a couple of minutes until you have melted cheese.
Serve warm, garnished with dried or chopped parsley or chives.
Video
Notes
Choose peppers with a flattish bottom so that they stand up during air frying. If you find your peppers are not standing nice, you can make tin foil nests for them.
Choose similar-sized peppers so they air fry at the same rate.
Don't overcrowd the Air Fryer so that air circulates and the food crisps up and cooks evenly. Make sure to leave space between each pepper.
Depending on the size of the peppers, you may have some filling left, for which you can just stuff another pepper.
Storage - keep stuffed peppers in an airtight container inside the fridge for 4 days.