For the lemon-spinach pesto, blend 2 3/4 cups spinach with the olive oil, garlic, and Parmesan in a food processor, adding more olive oil if mixture is too thick. Salt to taste.
2 Combine ricotta with lemon juice, pulp, and zest, then season with salt to taste. Beat mixture for approximately 3 minutes until smooth.
3 Preheat oven to 375 degrees and spray a 9x13 baking dish.
4 Spread 1/2 cup pesto over the bottom of baking pan. Top with 1/3 of cooked pasta, then 1/3 of ricotta mixture, then 1/3 pesto. Repeat layers. Top final layer with remaining spinach and then mozzarella.
5 Bake pasta, uncovered, for about 30 minutes or until hot and bubbly throughout. Turn oven to broil for 2-3 minutes to lightly brown cheese before removing from oven.
6 Let cool for 10 minutes before serving.