Preheat an oven, then coat a 9×13-inch baking dish with a little oil or nonstick spray. Bring a large pot of water to a rapid boil, then season generously with a few tablespoons of Kosher salt. Add dried ziti pasta, then cook according to package directions until al dente.
Heat olive oil in a large skillet or Dutch oven over medium-high heat. When hot, add Italian sausage, then use a spatula to break up into smaller pieces. Cook until browned. Add onion, then cook.
Stir in fresh oregano leaves, grated garlic, crushed red pepper flakes, and fennel seeds, then cook. Add tomato paste, then use a spatula to stir it into the onion and sausage.
Pour in red wine to deglaze the pan, then use a spatula to scrape any browned bits off the bottom. Cook until reduced by half, then add can of crushed tomatoes.
Stir in fresh baby spinach until wilted, then season with Kosher salt and black pepper. Pour in the drained ziti pasta, along with reserved pasta water. Stir well until the sauce evenly coats the pasta.
In a large bowl, mix together ricotta, grated Pecorino Romano, and lemon zest.
Pour half of the ziti and sausage mixture into the prepared baking dish, then dollop with half of the ricotta cheese and half of the mozzarella cheese.
Transfer to a preheated oven and bake until the cheese is bubbling. Adjust the oven temperature to broil, then carefully place the baked ziti on a rack. Broil. Allow the ziti to rest. Garnish with fresh basil or oregano leaves, then serve immediately!