In a large pot of boiling salted water, cook 1 pound of spaghettini, or thin spaghetti, until al dente according to package instructions.
Grate the zest of 1 lemon into a large pasta bowl. Juice the lemon, and add juice to the bowl. Stir in 1 stick butter, cut into small pieces, and 1 cup coarsely grated ricotta salata cheese or Parmesan.
Add drained pasta to lemon sauce, and sprinkle in 2 tablespoons thinly chopped fresh chives or scallion greens. Season with salt and pepper. Toss well, and serve.
This is one of my all-time favorite recipes. It's so easy and has flavors I love. We probably make this twice a month in the summer. So good!