Prep the squash: Trim the stem and bottom of each squash. Using a sharp knife, cut each squash into 1-cm thick slices. Cut each slice into long 0.5 to 1-cm thick strips.
Add the ricotta to a small food processor or blender and whip until smooth, 2 to 3 minutes. This will ensure the sauce has a silky consistency. The recipe will work if you decide to skip this step.
In a large pot (at least 4-quarts), add the squash, pasta, garlic, a big pinch of salt, and water. Bring to a boil. Reduce the heat to medium-high. Cook, stirring occasionally to ensure the pasta doesn’t stick to the bottom, for 5 to 6 minutes. The squash should be tender, while the pasta should be partially cooked and firm.
Add the parmesan, ricotta, parsley, the zest (2 teaspoons) and juice of a lemon (2 tablespoons). Using a pair of tongs or a large wooden spoon, vigorously stir until the pasta is coated in cheese. If needed, add an additional ½ cup of water at a time to help with the stirring and bringing the sauce together.
Continue cooking until the pasta is al dente and coated in a silky, creamy sauce, about 2 minutes. Taste and add more salt, as needed. Serve right away.
