We like fusilli for this recipe since its corkscrew shape does a nice job of trapping the sauce, but penne and campanelle also work well. In order for this recipe to be gluten-free, you must use gluten-free pasta.
Whisk 1 cup ricotta, 1 tablespoon oil, ¼ teaspoon pepper, and ⅛ teaspoon salt in medium bowl until smooth; set aside.
Bring 4 quarts water to boil in large pot. Add pasta and 1 tablespoon salt and cook, stirring often, until al dente. Reserve 1 cup cooking water. Stir spinach into pot with pasta and cook until wilted, about 30 seconds. Drain pasta and spinach and return them to pot.
While pasta cooks, heat remaining 2 tablespoons oil, garlic, nutmeg, and cayenne in saucepan over medium heat until fragrant, about 1 minute. Remove pan from heat and whisk in remaining ⅓ cup ricotta, cream, lemon zest and juice, and ¾ teaspoon salt until smooth.
Add ricotta-cream mixture and Parmesan to pasta and toss to combine. Let pasta rest, tossing frequently, until sauce has thickened slightly and coats pasta, 2 to 4 minutes, adjusting consistency with reserved cooking water as needed. Transfer pasta to serving platter, dot evenly with reserved ricotta mixture, and serve, passing extra Parmesan separately.
