Preheat your air fryer to 375 degrees Fahrenheit (190 degrees Celsius) while you get everything else ready.
Cut the woody ends off the asparagus spears and wash them thoroughly. Pat them dry with paper towels.
Add the asparagus spears to a large bowl and spray them with the cooking spray. Add the lemon juice, salt, pepper and garlic powder. Toss very well to coat.
Arrange the asparagus spears in a single layer in your air fryer, being careful to not over-crowd them. You might have to air fry in two batches.
Add 1/4 cup water at the bottom of your Air Fryer. If you don’t add the water, the asparagus will dry out and become brown and crispy. With the addition of the water, the asparagus will be bright green, tender and slightly browned and crisp on top.
Air fry at 375 F (190 C) for 5-7 minutes. Please keep in mind that the timing depends on your Air Fryer, how crowded your basket/tray is and how well done you prefer your asparagus.
Our favourite way to eat this asparagus is while it's still vibrant green, with a moist stem, a bit of a bite and a little browning on top. If you're not happy with how cooked your asparagus is after 5 minutes, shake your basket/tray and give it another minute or two.
Serve hot with some butter on top, if desired (optional).