Bring a large pan of water to the boil for the pasta.

Peel and dice the onion. Trim the celery to the palest bit, pull away any strings and dice that too. Put the onion and celery into a frying pan with the olive oil and a pinch of salt and then on to a medium- low flame and cook until soft, which will take a while.

Add the flaked tuna and capers, stir a minute, then add the wine and allow to bubble for 10 minutes, adding 3 tablespoons of lemon juice and some zest in the last minutes. It should be saucey – if it is watery, cook a bit longer.

Meanwhile cook the pasta until al dente, drain and tip into a warm serving bowl, tip the sauce on top, toss quickly, then add the yolk, toss again and serve.