Soak tomatoes in water for about 2 hours. Stone and roughly chop the olives. Pluck parsley leaves. Chop tomatoes and parsley very finely. Drain the tuna and put it in a bowl.
Add oil, tomatoes, olives and about 2 tablespoons of lemon juice. Mix with a fork and set aside. Put the pasta in plenty of boiling salted water and cook for 8-10 minutes until al dente. Drain the noodles and collect some cooking water.
Mix the pasta and tuna sauce, stretch with a little cooking water as required, arrange on plates and season with a few dashes of lemon juice. Sprinkle with parsley.