Add oil to a wok or large skillet over medium heat. Saute the red pepper flakes, garlic, and ginger, briefly, before adding the steak strips, red bell pepper, and celery.

Cook and stir for 3-5 minutes until the steak is fully browned on the outside.

Add the coconut aminos, vinegar, and cayenne pepper. Continue to cook and stir for about a minute.

Add the cashews and green onions, and cook until the steak is done.

Spoon equal portions of the mixture onto the lettuce leaves. Fold or roll the lettuce so that the mixture can be eaten by hand.