Preheat the air fryer: Set it to 400°F (200°C) for 3–5 minutes. A hot basket helps with browning.
Prep the squash: Rinse and dry well.
Trim the ends. Slice into 1/4-inch rounds or half-moons. Keep slices consistent for even cooking.
Toss with oil: Add zucchini and squash to a large bowl.
Drizzle with olive oil and toss to coat lightly and evenly.
Season: Sprinkle in garlic powder, onion powder, smoked paprika, salt, and pepper. Toss again so the spices cling to each piece. If using Parmesan, add half now and reserve half for after cooking.
Prepare the basket: Lightly spray the air fryer basket to reduce sticking.
Don’t overdo it.
Arrange in a single layer: Spread the slices in one even layer. A little overlap is fine, but don’t overcrowd. Work in batches if needed.
Air fry: Cook at 400°F (200°C) for 8–10 minutes, shaking the basket or flipping the slices halfway through.
Start checking at 7 minutes.
Check doneness: Look for golden edges and a crisp-tender bite. They should be soft in the center but not mushy.
Finish and serve: Toss with remaining Parmesan, a squeeze of lemon, or fresh herbs. Taste and adjust salt if needed.
Serve right away.