Spread ½ cup of marinara sauce evenly in the bottom of a 9x13-inch baking dish.
In a medium bowl, mix together the ricotta cheese, garlic, lemon zest, oregano, red pepper flakes, ½ teaspoon of salt, and several grinds of fresh pepper.
In a large pot of salted boiling water, cook the pasta according to the package instructions until al dente. Then drain the cooked pasta.
Return the pot to the stove and drizzle a small amount of olive oil onto the bottom of the pot. Add the spinach and sauté over low heat for 1 to 2 minutes, or until the spinach has just wilted. If needed, sauté the spinach in batches. Turn off the heat, remove the spinach from the pot, and gently squeeze out excess water. Coarsely chop the spinach and set it aside.
Add the cooked pasta back to the pot. Pour in the remaining marinara sauce, most of the chopped spinach, ¼ teaspoon of sea salt, and more fresh pepper. Toss the ingredients together until they are well combined.
Transfer half of the pasta mixture to the prepared baking dish. Place dollops of the ricotta mixture on top of the pasta, followed by the remaining chopped spinach. Then scoop the remaining pasta on top. Finish by sprinkling the mozzarella and pecor