Slice the beef eye round very, very thin. This is best achieved with a sharp knife and partially frozen beef. Place meat into a medium sized mixing bowl and add in the soy sauce, oyster sauce and black pepper. Allow this to marinate as you wash and prep the other ingredients.
Wash lettuce, slice tomatoes in half and cut cucumber into julienne pieces. Cilantro can be washed and left whole as the leaves can be picked off during the eating/lettuce making process.
Heat a large wok or large nonstick skillet over high heat until hot. Add avocado oil and swirl it around in the pan. Add garlic.
Then very quickly add the sliced beef and thinly sliced onions. Stir fry until the meat is cooked through about 5-7 minutes. Drizzle with sesame seed oil off the heat.
Squeeze the fresh lime juice into small bowls (½ tbsp lime juice, ⅛ tsp kosher salt per bowl and some fresh black pepper). You will use this to dip the lettuce wraps. Build lettuce wraps by adding some of the cooked beef, cilantro leaves, julienned cucumber and halved tomatoes. Dip into the lime sauce and enjoy!