1. Prepare the onions: Peel the yellow onions and slice them into 1/2-inch thick rings. Separate the rings gently so they cook more evenly in the air fryer.

2. Season the onions: In a large bowl, toss the sliced onion rings with olive oil, salt, and black pepper. Make sure each piece is lightly coated. This helps them crisp up and absorb flavor.

3. Arrange in the air fryer: Place the seasoned onion rings in a single layer in your air fryer basket. You may need to cook them in batches, depending on the size of your air fryer, to avoid overcrowding. Overcrowding can lead to steaming instead of crisping.

4. Air fry the onions: Cook at 375 F (190 C) for 15-20 minutes, shaking the basket every 5-7 minutes. Look for the onions to become tender, slightly browned, and caramelized at the edges. The cooking time can vary based on your air fryer model and onion thickness.

5. Prepare the garlic butter drizzle: While the onions are air frying, melt the unsalted butter in a small saucepan or microwave-safe bowl. Add the minced garlic to the melted butter and stir well.

6. Drizzle and serve: Once the onions are cooked to your liking, transfer them to a serving dish. Pour the warm garlic butter mixture evenly over the top of the onions. Garnish with fresh chopped parsley, if desired, and serve immediately.