Preheat the air fryer. Set it to 380°F (193°C) for 3–5 minutes.
A hot basket helps with browning.
Prep the sausage and veggies. Slice the sausage into 1/2-inch coins on a slight diagonal. Cut peppers and onion into similar-size strips for even cooking.
Toss with seasonings. In a large bowl, combine peppers, onion, and sausage. Drizzle with oil, then add Italian seasoning, garlic powder, smoked paprika, red pepper flakes, salt, and pepper.
Toss until evenly coated.
Load the air fryer basket. Spread the mix in a single layer if possible. If your air fryer is small, cook in two batches for best browning.
Cook. Air fry for 10–14 minutes, shaking the basket or stirring halfway. You’re aiming for crisp edges on the sausage and tender-crisp peppers.
Start checking at 10 minutes.
Finish and taste. When done, splash with red wine vinegar or lemon juice and toss. Adjust salt and pepper. Garnish with parsley if using.
Serve. Enjoy hot as-is, over cauliflower rice, in lettuce wraps, or alongside a simple salad.