Rinse the sushi rice under cold water until the water runs clear. Combine rice and water in a small pot. Bring to a boil, then reduce heat to low, cover, and simmer for 18 minutes. Remove from heat and let sit, covered, for 10 minutes.

Season the rice

In a small bowl, mix rice vinegar, sugar, and salt until dissolved. Gently fold the vinegar mixture into the cooked rice while fanning to cool. Set aside to cool to room temperature.

Tuna Mixture

In a bowl, combine diced ahi tuna, soy sauce, sesame oil, green onion, and sesame seeds. Mix gently and refrigerate until ready to use.

Fruit and Vegetable Layer

In a bowl, gently toss diced mango and avocado with lime juice and salt. Keep chilled.

Tempura Crunch

Make the batter

In a bowl, whisk together flour, cornstarch, and baking powder. Slowly add cold sparkling water and mix until just combined – batter should be slightly lumpy and cold.

Fry the crunch

Heat neutral oil in a small saucepan to 350°F (175°C). Drop spoonfuls of batter into the hot oil and fry until golden and crispy, about 2 minutes. Remove and drain on paper towels. Break into small crunchy pieces once cooled.

Sriracha Aioli

Whisk together mayonnaise, sriracha, and lime juice in a small bowl. Set aside.

Sweet Soy Drizzle

In a small saucepan, combine soy sauce, brown sugar, rice vinegar, and cornstarch mixed with water. Heat over medium heat, stirring constantly until thickened, about 2–3 minutes. Let cool slightly.

Assembly

Build the stack

Using a ring mold or small bowl lined with plastic wrap, layer ingredients in this order: 1/3 cup seasoned sushi rice (pressed down), fruit and vegetable mix, ahi tuna mixture, and a sprinkle of tempura crunch on top.

Garnish and serve

Carefully remove the mold or invert the bowl onto a plate. Drizzle with sriracha aioli and sweet soy reduction. Garnish with extra sesame seeds or microgreens if desired. Serve immediately.