Start by bringing a large pot of salted water to a rolling boil over high heat. Once boiling, add the rigatoni pasta and cook according to package instructions until al dente, typically 9-10 minutes.

While the pasta is cooking, heat a generous drizzle of olive oil in a wide pot over medium heat. Add the chopped yellow onion and crushed red pepper flakes, sautéing until the onion becomes translucent and soft, about 8-10 minutes.

Add the Italian sausage to the pot, breaking it apart. Cook for about 5-7 minutes, stirring occasionally, until browned and caramelized.

Once the sausage is golden brown, stir in the minced garlic and cook for an additional minute until fragrant.

Mix in the tomato paste until well combined, then add the halved grape tomatoes and a splash of white wine or chicken broth. Season with salt and black pepper to taste. Cook for about 10 minutes.

Stir in the zucchini and cook for another 5 minutes until it is tender.

Once the pasta is al dente, reserve about ½ cup of the cooking water before draining the rigatoni in a colander.

Return the drained rigatoni to the pot with the sauce, incorporating any reserved pasta water as needed to achieve your desired sauce consistency.

Finally, stir in the fresh basil and serve the rigatoni in bowls, topped with grated Parmesan cheese.