Peel and chop finely tomatoes. Peel and crush garlic. Wash and chop the parsley. Drain the tuna. Heat oil and fry tomatoes, garlic and half of parsley for 10 minutes at high heat. Season with salt and pepper. Add capers and simmer 1 hour. Do not cover the pot completely. From time to time stir. If necessary add some water. Meanwhile cook pasta in salted water. Drain, mix with the sauce and sprinkle with remaining parsley.