1. Cut flesh from mango half into small (about ¼-inch) dice. Measure and reserve 3 tablespoons of mango scraps.

2. Separate about one-third of the pineapple and cut into small dice, the same size as the mango dice. Combine diced mango and diced pineapple in a bowl and toss to combine.

3. Coarsely chop remaining pineapple and place in a blender along with reserved mango scraps and 1 teaspoon of the wasabi paste. Puree until smooth. Add yuzu juice (or grapefruit juice plus lime juice), fish sauce, cayenne pepper, and salt. Whir to combine. Taste. Puree should be tangy and pleasantly sweet; incorporate more mango for sweetness if necessary.

4. Place diced tuna in a bowl and season with salt and pepper. Add the pineapple-yuzu purée, diced mango, and diced cucumber, and toss to coat. Plate immediately: in the center of a plate, make a circle with a quarter of the tuna. If you have a round cookie cutter or ring mold, use it to build your stack. Place tiny dots of wasabi paste in a random pattern over the tuna. Spoon some diced mango and pineapple over the fish, and layer cucumber squares on top of the fruit. Garnish with the cilantro sprigs. Assemble 3 more appetizers and serve immediately.