Bring 6 quarts water and 2 teaspoons salt to a boil in a large stockpot. Stir in pasta; cook 12 minutes or until al dente. Drain pasta in a colander over a bowl, reserving 1/2 cup cooking water.
Combine remaining 1/2 teaspoon salt, Homemade Ricotta Cheese, 1/4 cup pecorino, oil, and 1/2 teaspoon pepper in a large bowl, stirring well. Add hot pasta, 1/4 cup reserved cooking water, and arugula; toss well to coat. Add additional cooking water if sauce is too thick. Spoon about 1 1/4 cups pasta mixture onto each of 8 plates. Top each serving with 1/4 cup tomato and 1 tablespoon pecorino. Sprinkle evenly with remaining 1/2 teaspoon pepper. Serve immediately.