Bring a large pot of salted water to a boil. Wash and dry all produce. Mince garlic. Trim ends from zucchini. Using a peeler, shave zucchini lengthwise into thin ribbons, rotating as you go, until you get to the seedy core; discard core.

Once water is boiling, add spaghetti to pot. Cook until al dente, 9-11 minutes. Reserve ½ cup pasta cooking water (1 cup for 4 servings), then drain.

While pasta cooks, remove sausage from casing; discard casing. Heat a drizzle of olive oil in a large pan over medium-high heat. Add sausage and cook, breaking up meat into pieces, until browned and cooked through, 4-6 minutes. Stir in garlic and Tuscan Heat Spice; cook until fragrant, 30 seconds.

Add marinara sauce to pan with sausage mixture and reduce heat to medium. Simmer until flavors meld and sauce is slightly reduced, 3-4 minutes.

Add spaghetti, ¼ cup reserved pasta cooking water (½ cup for 4 servings), and 1 TBSP butter (2 TBSP for 4) to pan with sauce. Toss to thoroughly combine. Separate zucchini ribbons with your hands, then stir into pasta until slightly softened, 1-2 minutes. Taste and season with salt and pepper. TIP: If needed, stir in more reserved pasta cooking water a splash at a time until spaghetti is thoroughly coated in sauce.

Divide pasta between bowls; top with Parmesan and serve.