Linguine with Butter, Pecorino, Arugula, and Black Pepper

From Every Day Pasta - Giada DeLaurentiis

1 lb linguine
1/4 C unsalted butter, at room temperature
1 1/4 C finely grated Pecorino Romano Cheese
1 1/2 tsp freshly ground black pepper
1 C coarsely chopped arugula
Salt, to taste

Bring a large pot of salted water to a boil over high heat. Add the linguine and cook until it is al dente, stirring frequently, about 8 minutes. Drain, reserving 1 1/2 cups of the pasta water.
Immediately toss the hot pasta in a large bowl with the butter to coat. While tossing the linguine, gradually sprinkle the cheese, pepper, and enough of the resreved pasta water evenly over the linguine to moisten. Add the arugula and toss to combine. Season the pasta with salt. Divide the pasta among 6 plates and serve.