Thinly slice the beef into paper-thin slices. See the above recipes notes for tips on how to do this easily. Once the meat is cut, marinate the meat in the coconut aminos, ½ tsp kosher salt, sesame seed oil, and fish sauce. Stir well to distribute the ingredients. Allow this mixture to sit while you prepare the other ingredients.
Thinly slice the white onion into julienne pieces. Mince the garlic. Preheat the Instant Pot on the Saute setting until it says hot. Once hot, add in the avocado oil, the white onions, and garlic. Saute for about one minute until the onions are translucent and browned slightly.
Next, add in the marinated beef. Stir well until all the onions are combined into the meat. Continue cooking in this manner until the meat is no longer pink. Some liquid will come off of the meat.
To thicken the mixture, sprinkle in two teaspoons of arrowroot starch. Stir the mixture very well to incorporate the starch and not form any lumps. Allow the mixture to come to a simmer again and to thicken the sauce.
Once thickened, serve the meat right away with freshly washed butter lettuce, sliced Roma tomatoes, sliced cucumber, and fresh cilantro. To eat, take a piece of lettuce and fill it with a small amount of meat, one slice of tomato, one slice of a cucumber, and some cilantro—dip in a lime dipping sauce. To make the dipping sauce, squeeze some lime juice into individual bowls and season to taste with salt and pepper.