Bring a large stock pot of salted water to a boil.  Add pasta and cook 6-8 minutes.  Before draining, reserve ½ cup of the pasta water.  

While the pasta is cooking, In a small bowl, combine ricotta, minced garlic, lemon juice and zest, ¼ cup parmesan cheese, salt and pepper.

Next reserve about a 1/2 cup of the pasta water. Drain the pasta and place in the skillet that the meatballs were cooked in.

Add the ricotta mixture to the pasta and toss to combine, adding a little of the reserved pasta water. This will not only add flavor, but the starch from the pasta water will help glue the pasta and sauce together.

Add the fresh spinach and toss until wilted.

Toss in remaining ¼ cup parmesan! Plate and serve with cooked meatballs and pine nuts.