Chop tuna to desired cube sizes and place in a mixing bowl.
In a separate mixing bowl, make marinade by adding minced shallots, sesame oil, tahini, soy sauce, capers, lemon juice, zest, and mix. Season with kosher salt and black pepper.
Pour the marinade over tuna. Allow to sit for 10-15 minutes.
Pour tuna into the center of a serving dish. Pour green goddess dressing around the border.
In a separate bowl, combine watercress, frisée, and truffle oil, then arrange over tuna.