Preheat your oven to 400°F (200°C).
In a large mixing bowl, combine the chicken pieces, pineapple chunks, bell peppers, red onion, olive oil, garlic, paprika, chili flakes, salt, and black pepper.
Toss everything together until evenly coated.
In a separate small bowl, whisk together soy sauce, pineapple juice, honey or brown sugar, vinegar, and the cornstarch mixed with water.
Pour the sauce over the chicken and vegetable mixture.
Toss again until everything is coated evenly.
Spread the Hawaiian Pineapple Chicken mixture onto a parchment-lined baking sheet in a single layer.
Bake for 25–30 minutes, stirring halfway through cooking.
Check that the chicken reaches an internal temperature of 165°F (74°C).
Remove from the oven and serve hot over steamed rice or noodles.
Garnish with fresh parsley, cilantro, or green onions if desired.