In a non stick pan or creuset heat the oil and fry the garlic and onion until fragrant, splash in the tomatoes, olives, capers, lemon and sugar and cook long enough for the flavours to mingle. Season with the salt and pepper.
Lastly add the tuna, (leaving it nice and chunky), basil and parsley and fold through.
Serve over hot pasta with a cheek of lemon on the side.