Bring a large pot of salted water to a rolling boil over high heat. Add spaghetti and cook according to package instructions for al dente, around 9–11 minutes.

While the pasta cooks, whisk together ricotta, lemon zest, lemon juice, grated garlic, olive oil, and black pepper in a mixing bowl until smooth.

Reserve about 1 cup of the starchy pasta water before draining the pasta.

Drain the pasta thoroughly. Return the hot pasta to the pot over low heat.

Add the ricotta sauce to the warm pasta and toss together for about 60–90 seconds. Stir in reserved pasta water if needed for consistency.

If using spinach, add it to the pot and toss for about 30 seconds to wilt.

Remove from heat and stir in Parmesan cheese. Adjust seasoning as needed.

Serve in warm bowls, garnished with extra Parmesan, basil, lemon zest, and a drizzle of olive oil.