Cut the tomatoes into slices 1/4 of an inch thick. Lay them on a cutting board and pat them dry with paper towels. Let the sit of 5 minutes.
3-4 green tomatoes
In one small bowl combine the flour, salt and pepper and stir.
1/2 cup flour, 1/2 teaspoon salt, 1/2 teaspoon pepper
In another bowl bread the egg and stir to mix the yolk and white.
1 egg
Combine the panko bread crumbs and cornmeal in a third bowl. Stir to mix.
1/2 cup cornmeal, 1/2 cup panko bread crumbs
Take a tomato slice and dip it into the flour, shaking off any excess. Then dip it into the egg, letting extra drip back into the bowl. Finally dip it in the bread crumb mixture. Make sure it gets thoroughly coated in bread crumbs. Place the coated green tomato on the cutting board.
Repeat with all the slices.
Take a mister bottle of oil and spray the coated slices with a thin layer of oil.
Preheat the air fryer at 400 F for 3 minutes.
Place the tomatoes in the air fryer basket, without overcrowding. You will probably have to make two batches.
Air fry at 400 F for 5 minutes. Then open up the air fryer and flip the slices over and spray this side with cooking oil. Air fry at 400 F for another 3 minutes.
Check the tomatoes. If they are golden brown and crispy they are done. If not put them put them back in for another 2 minutes and check again.
Notes
It is best not to use commercial spray oils because they can damage the non stick finish on the basket. A pump spray bottle with oil is easy to use and doesn't risk damaging the basket.
If you like you can add extra spices to the flour, like cayenne pepper for a spicy appetizer.
If you want to this keto friendly you could use a gluten free flour and pork rinds in place of bread crumbs. You could also skip the cornmeal and just use bread crumbs if you prefer.