Bring a large pot of heavily salted water to a rolling boil. Cook the rigatoni according to package directions until it reaches a perfect al dente texture—tender with a slight chew—ensuring the pasta holds its shape when tossed with the heavy pesto.

Drain the pasta and immediately rinse under cold running water to stop the cooking process and remove excess starch. This step is crucial for pasta salad to prevent the noodles from sticking together and to ensure the pesto coats every ridge without being absorbed instantly.

In a large mixing bowl, combine the cooled rigatoni with the kale pesto and sun-dried tomatoes. Toss thoroughly until the green sauce works its way into the center of the tubes, creating a glossy, herb-flecked coating on every piece of pasta.

Gently fold in the halved fresh mozzarella balls, taking care not to break them. For the best flavor profile, let the salad sit for at least 15 minutes before serving; this allows the sun-dried tomatoes to soften slightly and the mozzarella to soak up the aromatic basil and garlic notes.