1. Prepare the Lemony Ricotta Chicken Meatballs: In a large mixing bowl, combine the ground chicken, ricotta cheese, breadcrumbs, egg, chopped parsley, 2 cloves minced garlic, lemon zest, lemon juice, 1/2 cup grated Parmesan cheese, 1 teaspoon salt, and 1/2 teaspoon black pepper. Mix gently with your hands until just combined. Be careful not to overmix, as this can make the meatballs tough. Form the mixture into approximately 20-24 golf ball-sized meatballs.

2. Brown the Meatballs: Heat 1 tablespoon of olive oil in a large non-stick skillet or Dutch oven over medium-high heat. Carefully add the meatballs in batches, ensuring not to overcrowd the pan. Brown the meatballs on all sides for about 5-7 minutes until golden brown. They don’t need to be cooked through at this stage, as they will finish cooking in the oven. Transfer browned meatballs to a plate and set aside.

3. Cook the Pasta: Bring a large pot of salted water to a rolling boil. Add the penne or rigatoni pasta and cook according to package directions until al dente (slightly firm to the bite). This is crucial, as the pasta will continue to cook in the oven. Drain the pasta and set aside.

4. Prepare the Tomato Sauce: In the same skillet or Dutch oven (no need to clean it, the fond adds flavor!), heat 2 tablespoons of olive oil over medium heat. Add the chopped yellow onion and cook until softened, about 5-7 minutes. Add the remaining 3 cloves of minced garlic and cook for another minute until fragrant. Stir in the crushed tomatoes, tomato sauce, chicken broth, dried oregano, dried basil, and red pepper flakes (if using). Bring the sauce to a gentle simmer, then reduce heat to low, cover, and let it cook for at least 15 minutes to allow the flavors to meld. Season with salt and black pepper to taste.

5. Assemble the Pasta Bake: Preheat your oven to 375°F (190°C). To the simmering tomato sauce, add the fresh spinach and stir until it wilts, which should only take a couple of minutes. Gently fold in the cooked, drained pasta and the browned chicken meatballs. Mix well to ensure everything is evenly coated in the sauce. Transfer the entire mixture to a 9×13 inch baking dish. Sprinkle the shredded mozzarella cheese and the remaining 1/2 cup grated Parmesan cheese evenly over the top.

6. Bake to Golden Perfection: Bake the pasta bake for 25-30 minutes, or until the cheese is melted, bubbly, and golden brown, and the sauce is hot throughout. If the cheese is browning too quickly, you can loosely tent the dish with aluminum foil. Remove from oven and let it rest for 5-10 minutes before serving. Garnish with fresh basil or parsley, if desired.