To cook in air fryer: Preheat air fryer to 380 degrees.
In a small bowl, combine smoked paprika, garlic powder, onion powder, salt and chili powder.
In a medium bowl, add the beaten egg. Dip each chicken breast into the egg. Turn over and dip well to coat each breast. Next, place chicken on a plate. Sprinkle seasonings over all breasts. Turn over and sprinkle the other side.
Coat air fryer with olive oil spray. Add 2 chicken breasts to air fryer basket and cook turning halfway, until browned on the outside and cooked through, about 5 minutes per side. Repeat with the remaining 2 chicken breasts. If you have a large air-fryer, you can cook all 4 breasts at once.
To bake in oven: Preheat the oven to 350 degrees. Coat a large non-stick pan with olive oil spray. Follow step 3 above to prepare chicken breasts. Place all 4 breasts in the pan and cook for 2 minutes. Turn, and cook 2 minutes on other side. Place chicken breasts in a baking dish and place in the oven. Bake until no longer pink in the center about 8-10 minutes total.