Slice the onions evenly: Cut the onions into rings or half-moons approximately 1/8 inch (3 mm) thick. Separate the layers with your fingers. Consistent thickness is important: very thin pieces can burn before thicker slices become crisp.

Preheat the air fryer: Preheat the air fryer to 350°F (175°C) for 3 minutes. Lightly coat the basket with cooking spray.

Season with oil: Place the sliced onions in a large bowl. Drizzle with the avocado oil and toss thoroughly, separating any pieces that are stuck together. The onions should look lightly glossy but should not have oil pooling in the bowl.

Mix the dry coating: In a small bowl, combine the flour, cornstarch, salt, paprika, and black pepper. Stir until the mixture is evenly colored and no lumps of cornstarch remain.

Coat the onions: Sprinkle the flour mixture over the onions in two additions, tossing well after each addition. Separate the onion layers as you toss so the coating reaches as much surface area as possible. The onions should have a thin, dusty coating rather than a thick batter. If dry flour collects at the bottom of the bowl, continue tossing until most of it adheres.

Arrange the first batch: Transfer approximately one-third of the onions to the air fryer basket. Spread them into a loose, mostly even layer. A little overlap is acceptable, but the basket should not be tightly packed.

Begin air frying: Air fry at 350°F (175°C) for 5 minutes. Open the basket and use silicone-tipped tongs to toss and separate the onions, moving the darker pieces from the edges toward the center.

Cook until golden and crisp: Continue air frying for 5 to 7 minutes, tossing every 2 minutes. Remove individual pieces as they become deep golden brown. The onions may still feel slightly flexible when hot, but the coating should look dry and the edges should be crisp. Do not wait for every piece to become dark brown, as they continue to firm while cooling.

Cool the onions: Spread the cooked onions on a rimmed baking sheet or large plate in a single layer. Let them cool for 5 minutes. Avoid piling them while warm because trapped steam can soften the coating.

Cook the remaining batches: Repeat with the remaining onions, lightly spraying the basket again only if the coating begins to stick. Later batches may cook 1 to 2 minutes faster because the air fryer is fully heated.

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