Step 1: Cook the Rigatoni

1. Fill a large pot with water and add a generous pinch of salt. Bring it to a rolling boil.
2. Add the rigatoni pasta and cook according to the package instructions until al dente, about 10-12 minutes.
3. Reserve 1/2 cup of the pasta water before draining.
4. Drain the rigatoni and set it aside for later use.

Step 2: Sauté the Aromatics

1. Heat 2 tablespoons of olive oil in a large skillet over medium heat.
2. Add the finely chopped onion and cook for 4-5 minutes, stirring occasionally, until soft and translucent.
3. If you prefer a little spice, add 1/4 teaspoon of crushed red pepper flakes and stir.
4. Stir in the minced garlic and cook for 1-2 minutes, or until fragrant.

Step 3: Cook the Sausage

1. Remove the casing from the Italian sausage (if needed) and crumble it into the skillet.
2. Use a spoon to break the sausage into smaller pieces as it cooks.
3. Cook for 7-8 minutes, stirring occasionally, until browned and fully cooked.

Step 4: Add the Tomatoes and Tomato Paste

1. Stir in 3 tablespoons of tomato paste, mixing it thoroughly with the sausage mixture.
2. Add the grape tomatoes and cook for 2-3 minutes, allowing them to soften and release their juices.
3. Deglaze the skillet by pouring in 1 cup of white wine or chicken broth, scraping up any browned bits from the bottom.
4. Simmer for 3-4 minutes to reduce the liquid slightly.

Step 5: Incorporate the Zucchini

1. Add the diced zucchini to the skillet, along with the salt and black pepper.
2. Cook for 4-5 minutes until the zucchini is tender but still slightly firm, allowing it to absorb the flavors of the sauce.

Step 6: Combine the Pasta and Sauce

1. Return the cooked rigatoni to the skillet and toss it with the sauce until evenly coated.
2. If the sauce is too thick, add the reserved pasta water a little at a time, stirring until the desired consistency is reached.
3. Stir in the chopped fresh basil and drizzle the remaining tablespoon of olive oil over the dish for added richness.

Step 7: Serve

1. Divide the pasta among serving bowls or plates.
2. Garnish generously with freshly grated Parmesan cheese and additional basil leaves, if desired.
3. Serve immediately while hot and enjoy your hearty Italian feast!