Preheat your air fryer to 390ºF for at least 3 minutes, or according to your manufacturers instructions.
Add the sliced peppers and sliced onions to a large bowl and toss to combine.
Add in the smoked sausage slices.
Add in the avocado oil and toss everything together until well coated and evenly distributed.
Add half of the mixture into the basket of your air fryer (if you have a small model), and cook for 13-15 minutes, or until the sausage is warmed through and browned lightly.
Shake the basket at the halfway mark to encourage even cooking and browning.
Remove the cooked sausage and peppers from the air fryer basket with clean tongs, and repeat with the remaining half.
Serve and enjoy as is, or with pasta, marinara, or rice if desired.