HEAT avocado oil in a wok or skillet over medium-high heat. Add onions and cook until translucent.
ADD tempeh and cook, stirring frequently, until tempeh starts to brown.
ADD garlic, bell pepper, water chestnuts, and green onions, and cook 1 to 2 minutes until the peppers are just tender.
REDUCE heat to medium low and add in the peanut sauce. Stir and toss so everything is coated in sauce. Continue cooking for another minute to heat through, then remove from heat.
SCOOP the mixture into lettuce leaves and sprinkle peanuts and cilantro on top.