Cook the pasta as instructed on the package and preheat oven to 180° C.
Pour the olive oil into a pan to stir-fry the onion until it gets soft. Then, add the garlic, tomato paste, and oregano. Stir and cook for 2 more minutes, until slightly darkened.
Add crushed tomatoes, salt, and pepper. Stir and bring sauce to a simmer until it’s slightly reduced and flavors have melded. When done, remove from heat and stir in the basil.
Use a bowl to combine ricotta, spinach, lemon zest.
Mix the pasta with tomato sauce.
Now take a casserole and spread half of the pasta mixture on the bottom, then spread half of ricotta mixture, and finally sprinkle half of the cheeses on top. Repeat with the other half of mixtures and cheeses.
Cover the casserole with foil and bake until the cheese is bubbling, around 20-25 minutes. Garnish with more basil en serve.