Start to finish: 1 1/4 hours
1 ½ tablespoons extra-virgin olive oil
8 ounces baby spinach
1 cup whole milk ricotta
1 large egg, beaten lightly
½ ounce grated Parmigiano-Reggiano, plus extra to garnish the finished dish
1 ½ teaspoons grated lemon zest
¼ teaspoon kosher salt
¼ teaspoon black pepper
¾ cup all-purpose flour
2 cups marinara sauce
Bring a large pot of salted water to a boil.
In a large skillet heat the oil over high heat, add half the spinach and cook, stirring until it starts to wilt; add the second half with a pinch of salt, reduce the heat to medium high and cook, stirring until all of the spinach is wilted. Transfer the spinach to a strainer and let it cool. When it is cool enough to handle, working with a small handful at a time, squeeze the spinach with your hands to remove as much excess liquid as possible. Transfer the spinach to a cutting board, chop it fine and add it to a medium bowl along with the ricotta, egg, cheese, zest, salt and pepper. Stir until combined well. Sprinkle ¼ cup of the flour over the top of the mixture and fold it in, folding just until the mixture is combined.
Lightly sprinkle some of the remaining flour onto a small rimmed sheet pan and put the rest of the remaining flour into a pie plate or shallow dish. Scoop heaping teaspoons of the dough onto the flour in the pie plate, coat your hands with flour and roll the mounds of dough into balls (the dough will be very soft). Transfer each ball after you have shaped it to the sheet pan. You should end up with about 36 balls.
In a saucepan heat the marinara over medium heat until it is hot. Working in 2 batches add the dumplings to the boiling water and simmer them until they float (this will only take a few minutes). Transfer them as they are done to pasta bowls, top each portion with some of the sauce and sprinkle it with cheese.