Preheat the oven to 350°F (175°C).
Lightly coat the bottom and sides of a baking dish with cooking spray.
In a large bowl, combine the cooked whole-grain penne, shredded mozzarella, halved cherry tomatoes, marinara sauce, salt, and pepper; stir until evenly mixed.
Transfer the pasta mixture to the prepared baking dish, spreading it into an even layer.
Bake uncovered for about 20 minutes, or until the dish is bubbly and the cheese is melted.
Remove from the oven and sprinkle the torn basil leaves over the top before serving.