For the pork:
- 2 pork tenderloins (about 2 pounds), silver skin trimmed, cut into 1-inch-thick slices
- 1 tablespoon onion powder
- 1 teaspoon red pepper flakes
- 1 tablespoon freshly ground pepper
- 2 tablespoons chopped fresh ginger
- 1 tablespoon seeded and minced serrano chile
- 2 tablespoons minced fresh garlic
- 3 tablespoons soy sauce
- 2 tablespoons oyster sauce
- 1/2 teaspoon toasted sesame oil
For the salsa:
- 2 tablespoons rice vinegar
- 1/4 cup olive oil
- 1 tablespoon soy sauce
- 1/4 teaspoon toasted sesame oil
- 1 cup small (about 1/4 inch) watermelon cubes
- 1/4 English cucumber, seeded and cut into 1/4-inch cubes
- 1 Hass avocado, pitted, peeled and cut into 1/4-inch cubes
- 4 large, sturdy romaine-heart leaves, cut into 4-inch lengths (to resemble taco shells)
Combine all the pork ingredients in a re-sealable plastic bag and marinate for 30 minutes. Meanwhile, for the salsa, whisk together the rice vinegar, olive oil, soy sauce and sesame oil in a medium bowl. Gently fold in the watermelon, cucumber and avocado. Refrigerate until chilled.
Preheat a grill to medium heat. Remove the pork from the marinade, pat dry and grill for 2 minutes on one side. Turn and grill 1 more minute; remove from the heat and let rest 3 minutes before cutting into 1/2-inch pieces.
Fill the lettuce “shells” with pork, top with salsa and devour!