Step 1
Preheat a smoker to 225 degrees F (110 degrees C) according to manufacturer's instructions.
Step 2
Mix brown sugar and 1/4 cup salt together in a bowl.
Step 3
Score ahi tuna skin with a sharp knife; rub with brown sugar and salt mixture.
Step 4
Smoke tuna until an instant-read thermometer inserted into the center reads 140 degrees F to 155 degrees F (60 degrees C to 68 degrees C) about 1 hour.
Step 5
Mix masa corn flour and water together in a bowl until a slightly sticky dough forms. Divide dough into large balls.
Step 6
Heat a lightly oiled griddle over medium-high heat. Flatten balls of masa to 1/4-inch thickness and cook until golden brown 3 to 4 minutes per side. Cool sopes on a wire rack.
Step 7
Preheat a grill for medium-high heat and lightly oil the grate.
Step 8
Place tomatillos half the onion and 1 jalapeno pepper on the grill; cook until charred on all sides about 5 minutes. Transfer to a blender; blend into a smooth sauce. Season with salt.
Step 9
Dice remaining onion and jalapeno. Mix with tomatoes avocados and cilantro in a bowl. Season with lime juice and salt.
Step 9
Place cooked sopes on serving plates. Top with smoked tuna tomatillo sauce and avocado mixture. Garnish with shredded cabbage and queso fresco.