Cook the pasta according to the package directions. Drain and cover with foil to keep warm.
Meanwhile, in a large saucepan, whisk together the tomato sauce and pesto. Set the pan over medium heat and bring to a simmer. Reduce the heat to low and simmer for 10 minutes.
When the pasta has finished cooking, add it to the sauce and heat through. Season to taste with salt and black pepper.
Transfer the pasta to bowls and top with the mozzarella cheese.