Fill a large pot with water, add a generous pinch of salt, and bring it to a boil over high heat.

When the water is boiling, add the pasta shells to the pot and stir so they do not stick together.

Cook the shells until they are tender but still a little firm in the center, following the package time as a guide.

While the pasta cooks, set a large skillet on the stove over medium heat and add the olive oil.

Add the chopped onion to the skillet and cook, stirring often, until it softens and looks lightly golden at the edges, 4 to 5 minutes.

Add the chopped artichoke hearts to the skillet and cook for 2 minutes, stirring a few times, until they are hot and a few pieces pick up light color.

Turn the heat under the skillet to low and add the pieces of cream cheese.

Scoop about 3/4 cup of hot pasta water from the pot into the skillet. Stir until the cream cheese melts and the liquid turns into a smooth sauce.

Add the spinach to the skillet a handful at a time. Stir each handful until it wilts before adding the next one.

Stir 1/2 cup of the Parmesan, the lemon zest, the kosher salt, and the black pepper into the skillet. Keep stirring until the sauce looks creamy and evenly mixed.

Before draining the pasta, scoop out another 1/2 cup of pasta water and set it near the stove.

Drain the pasta shells in a colander.