Preheat your oven to 375°F (190°C).
In a large skillet, heat the sesame oil over medium heat. Add the ground chicken and cook until browned, about 5-7 minutes.
Stir in the garlic powder, ginger powder, salt, and pepper. Cook for an additional minute until fragrant.
Add the diced pineapple and teriyaki sauce to the skillet. Stir to combine and let simmer for 3-4 minutes.
Remove the skillet from heat and mix in the cooked rice and chopped green onions until well combined.
Cut the tops off the bell peppers and remove the seeds. Place them upright in a baking dish.
Stuff each bell pepper with the chicken and rice mixture, packing it down gently.
Cover the baking dish with aluminum foil and bake in the preheated oven for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, until the peppers are tender.
Garnish with sesame seeds if desired and serve warm.