Cut the beef tenderloin into thin slices and set aside
Cut the bell peppers and remove the seeds, then slice into thin strips. Add to a medium-sized bowl.
Slice onion into thin strips and add to the bowl with bell peppers.
Add 1 teaspoon of olive oil and 2 tablespoons of fajita seasoning to the bowl with the bell peppers and onions. Toss to coat.
Spread the seasoned vegetables in the bottom of the air fryer basket.
Transfer the beef to the same bowl you used for your vegetables and toss with 1 teaspoon of oil and 2 tablespoons of fajita seasoning. Spread the meat in an even layer over the top of the bell peppers and onions.
Place the basket in the air fryer and cook at 380 degrees for 10 minutes.
When the cook time is up, remove from the air fryer and serve in corn or flour tortillas.
Add toppings if desired: salsa, guacamole, sour cream, queso fresco and lime juice