Step 1

To make the dressing: Whisk together lime juice, fish sauce, sesame oil, sugar, and chili in a small bowl. Set aside.

Step 2

Place cashews in a small cast iron skillet over medium heat. Toast until fragrant and lightly browned, about 4 minutes. Transfer a medium bowl. Add onion, pineapple, and cilantro; toss to combine. Set aside.

Step 3

Light one chimney full of charcoal. When all the charcoal is lit and covered with gray ash, pour out and arrange the coals on one side of the charcoal grate. Set cooking grate in place, cover grill and allow to preheat for 5 minutes. Clean and oil the grilling grate. Score duck skin diagonally every 1/2-inch. Season breast liberally all over with salt and pepper. Place duck breast on hot side of grill, skin side down, and cook until skin has browned and crisped, 5 to 7 minutes. Flip and brown on other side, about 4 minutes. Move duck to cool side of grill, cover, and continue to cook until an instant read thermometer registers 130 degrees when inserted into middle of breast. Remove duck from grill and let rest for 5 to 10 minutes.

Step 4

Thinly slice duck, halving any long strips into bite-size pieces. Add duck into bowl with pineapple mixture. Pour on dressing and toss to combine. Transfer to plates and serve immediately.