Cook the pasta in a large pot of boiling salted water until tender but still firm to the bite, about 8 minutes.
Meanwhile, combine the tomato sauce, tuna, capers, and lemon peel in a heavy large skillet. Using a fork, break the tuna into chunks. Simmer to blend the flavors, about 5 minutes. Season with salt and pepper, to taste.
Drain the pasta, reserving 1 cup of the cooking liquid. Add the pasta to the sauce and toss to coat. Toss the pasta with enough reserved cooking liquid to moisten. Stir in the parsley and serve.