Bring a large saucepan of water to the boil. Add a generous amount of salt and cook the spaghetti until al dente or according to the package instructions.

Meanwhile, place the ricotta cheese in a bowl large enough to hold all the pasta and mash it with the back of a spoon until smooth.

Stir in the Parmigiano Reggiano cheese and almost all of the grated lemon zest, reserving a little for serving. Season with salt and pepper to taste.

Add ¼ cup of the pasta water and mix to combine. Add more pasta water as needed to create a soft, creamy consistency. Depending on the ricotta, this could take up to 1 cup of water.

Before draining the spaghetti, reserve 1 cup of the pasta water. Drain the spaghetti and add it to the bowl with the sauce.

Toss well to combine, adding more reserved pasta water if needed to loosen the sauce and help it coat the pasta. The heat from the spaghetti will warm the sauce.

For a warmer, creamier sauce, set the bowl over the saucepan of simmering water and toss briefly until silky. Alternatively, return the pasta and sauce to the empty saucepan and stir over low heat for a few seconds. Do not overheat.

Serve with the reserved lemon zest and freshly ground black pepper sprinkled over each plate.