1. 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. This step is crucial for easy cleanup and preventing sticking.

2. 2. Season the Chicken: In a medium bowl, combine the cubed chicken breasts with olive oil, Italian seasoning, garlic powder, salt, and black pepper. Toss well to ensure all the chicken pieces are evenly coated. The chicken should look lightly glistening and fragrant with herbs.

3. 3. Prepare the Vegetables: On the prepared baking sheet, arrange the broccoli florets, red bell pepper pieces, and red onion wedges. Drizzle them with a little extra olive oil, if desired, and a pinch of salt and pepper. Spread them out in a single layer.

4. 4. Combine and Arrange on the Sheet Pan: Add the seasoned chicken to the baking sheet with the vegetables. Toss everything gently together on the pan to ensure an even distribution. Make sure the ingredients are spread out in a single layer, not overcrowded, so they roast rather than steam.

5. 5. Initial Roasting: Place the baking sheet in the preheated oven and roast for 15 minutes. The chicken should start to turn opaque and the vegetables will begin to soften and lightly brown at the edges.

6. 6. Add Tomatoes and Final Roasting: Remove the sheet pan from the oven. Add the halved cherry tomatoes to the pan and gently toss everything once more. Sprinkle the grated Parmesan cheese evenly over the chicken and vegetables. Return the pan to the oven and continue roasting for another 10-15 minutes, or until the chicken is cooked through (internal temperature of 165 F (74 C)) and the vegetables are tender-crisp with some caramelized edges. The cheese should be melted and slightly golden.

7. 7. Serve Immediately: Once cooked, remove the sheet pan from the oven. Let it rest for a couple of minutes before serving directly from the pan or transferring to individual plates.