Most air fryers' max temp is 400 F, so that's what we'll do it on. Preheat your air fryer for a few minutes.

I've tried a number of pan lining methods but nothing has worked terribly well (see notes & pics in post). So usually now I just do some non-stick spray or grease with butter. I use a 6" cake pan as that's what fits in my air fryer.

In a bowl measure the sugar and add the orange zest. Rub them together with your fingers until your have orange zest sugar (this releases the flavorful oils).

Pour all the ingredients into a food processor (my 8-cup works best for this) fitted with the blade attachment.

Process the batter until it’s smooth and lump-free, about 5 minutes (yes, this long!), scraping around the bowl about halfway through.

Pause the air fryer, place the pan inside, and pour the batter into the prepared pan.

Carefully close the air fryer and bake at 400 F (on air fryer mode, if you have multiple) for 20-25 minutes. Start checking at the 18-minute mark, you're looking for a top that's deep-dark brown (burnt-looking), the edges just set, the center still fairly jiggly, and a digital thermometer inserted 1" from the edge and 1" down should just barely read 185°F. Check often from here on out, it tips over 20+ degrees very fast!

Remove the pan from the air fryer safely (I use 2 sets of silicone tongs) and place on a rack to cool to room temperature.

I unmold by running a knife around the edges, then carefully flipping into my hand and quickly onto a plate. Serve at room temp for the best texture, but it's delicious (but more dense) cold.