Cut the onion into ¼-½-inch (0.64-1.27 cm) thick rings. Carefully split the rings apart, saving the middles of the onions for another recipe.
Line two large baking sheets with freezer paper.
You will be putting the breading mixture in three small bowls. Fill each bowl with the ingredients shown, and refill them as needed as you coat the rings. This is VERY important to help prevent the dry coatings from getting clumpy. Don't skip doing this!
Bowl 1: ¼ cup almond flour and ½ teaspoon paprika. Stir. (I needed to refill this bowl 4 times.)
Bowl 2: Whisk 2 eggs. (I needed to refill this bowl 3 times.)
Bowl 3: 1½ cups pork panko, 1 teaspoon garlic powder, ½ teaspoon onion powder, pinch of cayenne pepper. (I needed to refill this bowl twice. If you use a different amount of the breading ingredients than I did, the nutrition information below will be incorrect.)
Bread the cut onions by dipping them in bowl 1, bowl 2, bowl 1, bowl 2, then bowl 3. If the unbreaded onion rings are dry, you can skip a step and bread them like this: bowl 2, bowl 1, bowl 2, then bowl 3. Coat all the onion rings well with the breading.
Lay the coated onion rings in a single layer on the lined baking sheets. Try to ensure that they are not touching. However, it's fine if you place the small-diameter onion rings inside of the larger ones.
After you have all of the breaded keto onion rings on the trays, freeze them for at least 4 hours. The freezing step helps ensure the coating won't fall off when we air fry.
After the onion rings have frozen solid, air fry what you'll eat and pack the rest of the frozen onion rings in freezer storage bags for later.
To air fry onion rings, put the rings in a single layer on the air fryer tray(s). Small onion rings can be put inside of larger ones, but try to ensure they don’t touch. I was only able to fit a maximum of 10 onion rings per tray.
Air frying on one tray: air fry in the top rack position at 400°F (200°C) for 10 minutes. No need to flip them.
Air frying on two trays: air fry for 7 minutes at 400°F (200°C). Then switch the position of the trays in the air fryer oven and cook an additional 6-7 minutes at 400°F (200°C). (13-14 minutes total air frying time)
Let the onion rings cool a little before serving with your favorite dipping sauce. Enjoy!