Bring 4 quarts water to boil in large pot over high heat. Add rice and onion. Boil until rice is just tender, about 16 minutes. Drain, reserving 1/2 cup cooking liquid. Mix parsley, butter, basil, lemon juice, and lemon peel in large bowl. Add hot rice mixture; stir to melt butter. Add reserved 1/2 cup cooking liquid and 1 cup cheese; stir. Season with salt and pepper. Sprinkle with 2 tablespoons cheese. Garnish with basil sprigs and serve.