1. Toast the pine nuts in a dry skillet over medium-low heat for 3 to 5 minutes, stirring often, until lightly golden. Transfer to a bowl.

2. Bring a large pot of salted water to a boil. Cook the pasta until al dente, then reserve 1 cup pasta water before draining.

3. Warm olive oil in a large skillet over medium-low heat. Add garlic and red pepper flakes, then cook for 30 to 60 seconds until fragrant.

4. In a bowl, mix ricotta, Parmesan, lemon zest, lemon juice, salt, black pepper, and 1/2 cup reserved pasta water until smooth.

5. Add the drained hot pasta to the skillet with the garlic oil. Add spinach and toss until wilted.

6. Turn the heat off or keep it very low. Add the lemon ricotta sauce and toss until the pasta is creamy and coated.

7. Add more reserved pasta water as needed to loosen the sauce.

8. Serve warm with toasted pine nuts, fresh herbs, extra Parmesan, and more lemon zest if desired.