In a large mixing bowl, combine the ranch dressing, garlic powder, onion powder, salt, and pepper. Mix until well blended.
Place the chicken breasts in a 9x13 inch baking dish and pour the ranch mixture over them, ensuring they are thoroughly coated.
Scatter the broccoli florets and halved cherry tomatoes around the chicken in the baking dish.
Cover the baking dish with aluminum foil and bake in the preheated oven for 25 minutes.
After 25 minutes, remove the foil and sprinkle the shredded cheddar cheese evenly over the chicken and vegetables.
Return the dish to the oven (uncovered) and bake for an additional 15-20 minutes, or until the chicken is cooked through and reaches an internal temperature of 165°F (75°C).
Remove from the oven and allow it to rest for 5 minutes. Top with chopped green onions and optionally garnish with fresh parsley before serving.