Cook the pasta: Bring a large pot of salted water to a boil. Add the pasta and cook according to the package instructions until al dente. Drain and set aside.
Sauté the onion and garlic: In a large pan, heat the olive oil over a low to medium heat. Add the diced onion and garlic and sauté until softened, about 5 minutes.
Add the tomatoes and seasoning: Pour in the tinned tomatoes, sun-dried tomatoes, and oregano. Stir and let the mixture simmer for 5 minutes.
Incorporate the spinach: Stir in the fresh spinach and cook until wilted, about 2-3 minutes. Stir regularly.
Stir in the mascarpone: Add the mascarpone cheese and stir until hot and well-combined.
Finish with lemon and parsley: Add the lemon zest, lemon juice and parsley to the sauce, and season with salt and pepper to taste.
Coat the pasta: Toss in the cooked pasta, stirring to coat the pasta in the sauce.
Serve: Plate the pasta and garnish with extra parsley and a light drizzle of olive oil if desired.