Adjust rack to top position and preheat oven to 450 degrees. Bring a large pot of salted water to a boil. Wash and dry produce.

Trim and halve zucchini lengthwise; slice crosswise into ½-inch-thick half-moons. Halve, peel, and thinly slice onion.

Toss zucchini on a baking sheet with a drizzle of oil, half the Italian Seasoning (you’ll use the rest later), and a pinch of salt and pepper.

Roast on top rack, tossing halfway through, until browned and tender, 14-16 minutes.

Tent with foil to keep warm.

Once water is boiling, add cavatappi to pot. Cook, stirring occasionally, until al dente, 9-11 minutes.

Reserve 1½ cups pasta cooking water (2 cups for 4 servings), then drain.

While pasta cooks, heat a drizzle of oil in a large pan over medium-high heat. Add onion and a pinch of salt and pepper. Cook, stirring occasionally, until softened, 5-6 minutes.

Add sausage* and cook, breaking up meat into pieces, until browned, 3-4 minutes (it’ll finish cooking in the next step).

Add tomato paste and remaining Italian Seasoning to pan. Cook, stirring constantly, until fragrant, 1 minute.

Stir in stock concentrate, 1 cup reserved pasta cooking water (1½ cups for 4 servings), and a big pinch of salt and pepper. Bring to a simmer; cook until sauce has slightly thickened and sausage is cooked through, 2-3 minutes.

Reduce heat to medium low.

Stir drained cavatappi, roasted zucchini, sour cream, and 1 TBSP butter (2 TBSP for 4 servings) into pan until thoroughly combined. TIP: If needed, stir in more reserved cooking water, a splash at a time, until pasta is coated in a creamy sauce.

Divide pasta between bowls. Sprinkle with Parmesan and serve.