In a small bowl, stir together the Ponzu (1/4 cup), Mirin (1 tablespoon), Honey (1 tablespoon) and Sesame Oil (2 tablespoon).
Spread the Sesame Seeds (1/2 cup) out on a plate.
Coat the Fresh Tuna Steak (4) with the sauce mixture, then press into the sesame seeds to coat.
Oil the cooking grates well or using a cast iron skillet over high heat until very hot.
Place steaks in the pan, and sear for about 30 seconds on each side. If cooking on a grill use Grill Grates at a temp of at least 500 degrees F (260 degrees C) and sear for 1min each side.
Slice the tuna into slices and brush with remaining sauce mixture.
To make the wasabi guacamole, use a fork to mash the Hass Avocado (2) in a large bowl.
Stir in the Onion (1), Tomato (1), Ponzu (3 tablespoon), Hot Sauce (1 teaspoon), Worcestershire Sauce (1/2 teaspoon), Kosher Salt (1 teaspoon),Ground Black Pepper (1/4 teaspoon), and Wasabi Powder (1 teaspoon). Mix well; taste, and add additional salt and pepper if necessary.
Place guacamole in serving bowl and garnish with Scallion (1) and Fresh Cilantro (to taste). Cover and refrigerate for 1 hour to allow flavors to blend.
To make the ponzu cucumbers & onions, chop Onion (1/2) and Cucumber (2) into bite-sized pieces.
Mix Sesame Oil (1 teaspoon), Sesame Seeds (to taste), Ponzu (4 1/2 teaspoon) and Rice Vinegar (1 tablespoon) and submerge onions and cucumbers.
Set in fridge for at least 1 hour before serving.
Serve Tuna, Wasabi Guacamole and Cucumbers and Onions with tacos.