1. Preheat Your Oven and Prepare the Pan: Start by preheating your oven to 400 F (200 C). Line a large baking sheet with parchment paper or aluminum foil for easier cleanup. This step is crucial for preventing sticking and making post-dinner tidying a breeze.

2. Season the Chicken: In a medium bowl, toss the cut chicken pieces with 1 tablespoon of olive oil, 1/2 teaspoon of Italian seasoning, 1/4 teaspoon of garlic powder, 1/4 teaspoon of onion powder, 1/8 teaspoon of salt, and 1/8 teaspoon of black pepper. Ensure the chicken is evenly coated.

3. Prepare and Season the Vegetables: In a separate large bowl, combine the broccoli florets, bell pepper pieces, and red onion wedges. Drizzle with the remaining 1 tablespoon of olive oil, 1/2 teaspoon of Italian seasoning, 1/4 teaspoon of garlic powder, 1/4 teaspoon of onion powder, 1/8 teaspoon of salt, and 1/8 teaspoon of black pepper. Toss well until all the vegetables are lightly coated.

4. Arrange on the Sheet Pan: Spread the seasoned chicken and vegetables in a single layer on the prepared baking sheet. Make sure not to overcrowd the pan, as this can steam the ingredients instead of roasting them, preventing them from getting beautifully caramelized. If necessary, use two baking sheets.

5. Roast to Perfection: Place the baking sheet in the preheated oven and roast for 15 minutes.

6. Add Cherry Tomatoes (Optional) and Finish Roasting: After 15 minutes, if using, add the cherry tomatoes to the pan and gently toss everything. Return the pan to the oven and continue roasting for another 5-10 minutes, or until the chicken is cooked through (internal temperature reaches 165 F / 74 C) and the vegetables are tender-crisp and slightly browned. The chicken should no longer be pink in the center, and the vegetables should have a nice char.

7. Serve Immediately: Remove the pan from the oven. Garnish with fresh chopped parsley, if desired, and serve hot.