Preheat your oven to 400°F (200°C). Lightly grease a large baking sheet with oil or cooking spray.
In a small bowl, whisk together the pineapple juice, soy sauce, brown sugar, minced garlic, ginger, and cornstarch slurry until well combined.
Place the cubed chicken, pineapple chunks, bell peppers, and red onion onto the prepared baking sheet. Drizzle with olive oil and toss lightly to coat.
Pour the sauce mixture over the ingredients on the pan. Toss everything again until the chicken and vegetables are evenly coated in the glaze. Spread them out in a single layer to ensure even cooking.
Bake for 20-25 minutes, or until the chicken is cooked through (internal temperature of 165°F) and vegetables are tender-crisp.
Optional: Turn the oven to broil for the last 2-3 minutes to caramelize the pineapple and edges of the chicken. Watch closely to prevent burning.
Remove from the oven and garnish with sliced green onions and sesame seeds. Serve immediately over white rice or cauliflower rice.