Cook the pasta in salted water according to package instructions until tender.
Peel and finely chop the onions and garlic. Wash parsley and chop finely as well.
Drain the tuna.
Now mix the pasta with the chopped tuna, mayonnaise, onion, garlic and parsley.
Season well with salt, pepper and lemon juice and leave in the refrigerator for an hour.
Serve the salad at room temperature.