In a medium bowl, combine the brown sugar, soy sauce, garlic powder, ginger powder, and a pinch of salt and pepper. Whisk until the sugar is dissolved and the marinade is well mixed.
Place the chicken breasts in a large zip-lock bag and pour the marinade over them. Seal the bag, ensuring the chicken is well coated, and refrigerate for at least 30 minutes (or up to 4 hours for more flavor).
Preheat your oven to 375°F (190°C). In a large oven-safe skillet, heat the olive oil over medium-high heat.
Remove the chicken from the marinade and reserve the marinade for later. Sear the chicken breasts in the hot skillet for about 3-4 minutes on each side, until golden brown.
Pour the reserved marinade and diced pineapple over the chicken in the skillet. Bring the mixture to a simmer.
Transfer the skillet to the preheated oven and bake for 20-25 minutes, or until the chicken is cooked through (internal temperature should reach 165°F or 75°C).
Once done, remove from the oven and let it rest for 5 minutes before serving.
Garnish with sliced green onions and sesame seeds before serving.
Notes
For best flavor, marinate the chicken for up to 4 hours.